Component carrier (de)activation in communication systems using carrier aggregation

ABSTRACT

This invention relates to the proposal of component carrier (de)activation message that is allowing a activation or deactivation of one or more component carriers in the uplink or downlink. Furthermore, the invention relates to the use of the new component carrier (de)activation message in methods for (de)activation of downlink component carrier(s) configured for a mobile terminal, a base station and a mobile terminal. To enable efficient and robust (de)activation of component carriers, the invention proposes to use component carrier-specific or cell-RNTI(s) for the scrambling of the CRC of the component carrier (de)activation message, and to explicitly indicate the intended recipient of the component carrier (de)activation message in a corresponding field in the message. Furthermore, the invention further proposes different designs of the component carrier (de)activation message and further uses thereof, so as to trigger CQI reporting and/or SRS transmission by a mobile terminal.

FIELD OF THE INVENTION

This invention relates to the proposal of component carrier(de)activation message that is allowing an activation or deactivation ofone or more component carriers in the uplink or downlink. Furthermore,the invention relates to the use of the new component carrier(de)activation message in methods for (de)activation of downlinkcomponent carrier(s) configured for a mobile terminal, a base stationand a mobile terminal.

TECHNICAL BACKGROUND Long Term Evolution (LTE)

Third-generation mobile systems (3G) based on WCDMA radio-accesstechnology are being deployed on a broad scale all around the world. Afirst step in enhancing or evolving this technology entails introducingHigh-Speed Downlink Packet Access (HSDPA) and an enhanced uplink, alsoreferred to as High Speed Uplink Packet Access (HSUPA), giving aradio-access technology that is highly competitive.

In order to be prepared for further increasing user demands and to becompetitive against new radio access technologies 3GPP introduced a newmobile communication system which is called Long Term Evolution (LTE).LTE is designed to meet the carrier needs for high speed data and mediatransport as well as high capacity voice support to the next decade. Theability to provide high bit rates is a key measure for LTE.

The work item (WI) specification on Long-Term Evolution (LTE) calledEvolved UMTS Terrestrial Radio Access (UTRA) and UMTS Terrestrial RadioAccess Network (UTRAN) is to be finalized as Release 8 (LTE). The LTEsystem represents efficient packet-based radio access and radio accessnetworks that provide full IP-based functionalities with low latency andlow cost. The detailed system requirements are given in. In LTE,scalable multiple transmission bandwidths are specified such as 1.4,3.0, 5.0, 10.0, 15.0, and 20.0 MHz, in order to achieve flexible systemdeployment using a given spectrum. In the downlink, Orthogonal FrequencyDivision Multiplexing (OFDM) based radio access was adopted because ofits inherent immunity to multipath interference (MPI) due to a lowsymbol rate, the use of a cyclic prefix (CP), and its affinity todifferent transmission bandwidth arrangements. Single-Carrier FrequencyDivision Multiple Access (SC-FDMA) based radio access was adopted in theuplink, since provisioning of wide area coverage was prioritized overimprovement in the peak data rate considering the restrictedtransmission power of the user equipment (UE). Many key packet radioaccess techniques are employed including multiple-input multiple-output(MIMO) channel transmission techniques, and a highly efficient controlsignaling structure is achieved in LTE (Release 8).

LTE Architecture

The overall architecture is shown in FIG. 1 and a more detailedrepresentation of the E-UTRAN architecture is given in FIG. 2. TheE-UTRAN consists of eNodeB, providing the E-UTRA user plane(PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towardsthe user equipment (UE). The eNodeB (eNB) hosts the Physical (PHY),Medium Access Control (MAC), Radio Link Control (RLC), and Packet DataControl Protocol (PDCP) layers that include the functionality ofuser-plane header-compression and encryption. It also offers RadioResource Control (RRC) functionality corresponding to the control plane.It performs many functions including radio resource management,admission control, scheduling, enforcement of negotiated uplink Qualityof Service (QoS), cell information broadcast, ciphering/deciphering ofuser and control plane data, and compression/decompression ofdownlink/uplink user plane packet headers. The eNodeBs areinterconnected with each other by means of the X2 interface.

The eNodeBs are also connected by means of the S1 interface to the EPC(Evolved Packet Core), more specifically to the MME (Mobility ManagementEntity) by means of the S1-MME and to the Serving Gateway (SGW) by meansof the S1-U. The S1 interface supports a many-to-many relation betweenMMEs/Serving Gateways and eNodeBs. The SGW routes and forwards user datapackets, while also acting as the mobility anchor for the user planeduring inter-eNodeB handovers and as the anchor for mobility between LTEand other 3GPP technologies (terminating S4 interface and relaying thetraffic between 2G/3G systems and PDN GW). For idle state userequipments, the SGW terminates the downlink data path and triggerspaging when downlink data arrives for the user equipment. It manages andstores user equipment contexts, e.g. parameters of the IP bearerservice, network internal routing information. It also performsreplication of the user traffic in case of lawful interception.

The MME is the key control-node for the LTE access-network. It isresponsible for idle mode user equipment tracking and paging procedureincluding retransmissions. It is involved in the beareractivation/deactivation process and is also responsible for choosing theSGW for a user equipment at the initial attach and at time of intra-LTEhandover involving Core Network (CN) node relocation. It is responsiblefor authenticating the user (by interacting with the HSS). TheNon-Access Stratum (NAS) signaling terminates at the MME and it is alsoresponsible for generation and allocation of temporary identities touser equipments. It checks the authorization of the user equipment tocamp on the service providers Public Land Mobile Network (PLMN) andenforces user equipment roaming restrictions. The MME is the terminationpoint in the network for ciphering/integrity protection for NASsignaling and handles the security key management. Lawful interceptionof signaling is also supported by the MME. The MME also provides thecontrol plane function for mobility between LTE and 2G/3G accessnetworks with the S3 interface terminating at the MME from the SGSN. TheMME also terminates the S6a interface towards the home HSS for roaminguser equipments.

Component Carrier Structure in LTE (Release 8)

The downlink component carrier of a 3GPP LTE (Release 8) is subdividedin the time-frequency domain in so-called sub-frames. In 3GPP LTE(Release 8) each sub-frame is divided into two downlink slots as shownin FIG. 3, wherein the first downlink slot comprises the control channelregion (PDCCH region) within the first OFDM symbols. Each sub-frameconsists of a give number of OFDM symbols in the time domain (12 or 14OFDM symbols in 3GPP LTE (Release 8)), wherein each of OFDM symbol spansover the entire bandwidth of the component carrier. The OFDM symbols arethus each consists of a number of modulation symbols transmitted onrespective N_(RB) ^(DL)×N_(sc) ^(RB) subcarriers as also shown in FIG.4.

Assuming a multi-carrier communication system, e.g. employing OFDM, asfor example used in 3GPP Long Term Evolution (LTE), the smallest unit ofresources that can be assigned by the scheduler is one “resource block”.A physical resource block is defined as N_(symb) ^(DL) consecutive OFDMsymbols in the time domain and N_(sc) ^(RB) consecutive subcarriers inthe frequency domain as exemplified in FIG. 4. In 3GPP LTE (Release 8),a physical resource block thus consists of N_(symb) ^(DL)×N_(sc) ^(RB)resource elements, corresponding to one slot in the time domain and 180kHz in the frequency domain (for further details on the downlinkresource grid, see for example 3GPP TS 36.211, “Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical Channels and Modulation(Release 8)”, version 8.9.0 or 9.0.0, section 6.2, available athttp://www.3gpp.org and incorporated herein by reference).

Layer 1/Layer 2 (L1/L2) Control Signaling

In order to inform the scheduled users about their allocation status,transport format and other data related information (e.g. HARQinformation, transmit power control (TPC) commands), L1/L2 controlsignaling is transmitted on the downlink along with the data. L1/L2control signaling is multiplexed with the downlink data in a sub-frame,assuming that the user allocation can change from sub-frame tosub-frame. It should be noted that user allocation might also beperformed on a TTI (Transmission Time Interval) basis, where the TTIlength is a multiple of the sub-frames. The TTI length may be fixed in aservice area for all users, may be different for different users, or mayeven by dynamic for each user. Generally, the L1/2 control signalingneeds only be transmitted once per TTI. The L1/L2 control signaling istransmitted on the Physical Downlink Control Channel (PDCCH). It shouldbe noted that in 3GPP LTE, assignments for uplink data transmissions,also referred to as uplink scheduling grants or uplink resourceassignments, are also transmitted on the PDCCH.

With respect to scheduling grants, the information sent on the L1/L2control signaling may be separated into the following two categories.

Shared Control Information (SCI) Carrying Cat 1 Information

The shared control information part of the L1/L2 control signalingcontains information related to the resource allocation (indication).The shared control information typically contains the followinginformation:

-   -   A user identity indicating the user(s) that is/are allocated the        resources.    -   RB allocation information for indicating the resources (Resource        Blocks (RBs)) on which a user(s) is/are allocated. The number of        allocated resource blocks can be dynamic.    -   The duration of assignment (optional), if an assignment over        multiple sub-frames (or TTIs) is possible.

Depending on the setup of other channels and the setup of the DownlinkControl Information (DCI)—see below—the shared control information mayadditionally contain information such as ACK/NACK for uplinktransmission, uplink scheduling information, information on the DCI(resource, MCS, etc.).

Downlink Control Information (DCI) Carrying Cat 2/3 Information

The downlink control information part of the L1/L2 control signalingcontains information related to the transmission format (Cat 2information) of the data transmitted to a scheduled user indicated bythe Cat 1 information. Moreover, in case of using (Hybrid) ARQ as aretransmission protocol, the Cat 2 information carries HARQ (Cat 3)information. The downlink control information needs only to be decodedby the user scheduled according to Cat 1. The downlink controlinformation typically contains information on:

-   -   Cat 2 information: Modulation scheme, transport-block (payload)        size or coding rate, MIMO (Multiple Input Multiple        Output)-related information, etc. Either the transport-block (or        payload size) or the code rate can be signaled. In any case        these parameters can be calculated from each other by using the        modulation scheme information and the resource information        (number of allocated resource blocks)    -   Cat 3 information: HARQ related information, e.g. hybrid ARQ        process number, redundancy version, retransmission sequence        number

Downlink control information occurs in several formats that differ inoverall size and also in the information contained in its fields. Thedifferent DCI formats that are currently defined for LTE Release 8/9(3GPP LTE) are described in detail in 3GPP TS 36.212, “Multiplexing andchannel coding (Release 9)”, version 8.8.0 or 9.0.0, section 5.3.3.1(available at http://www.3gpp.org and incorporated herein by reference).

Downlink & Uplink Data Transmission

Regarding downlink data transmission, L1/L2 control signaling istransmitted on a separate physical channel (PDCCH), along with thedownlink packet data transmission. This L1/L2 control signalingtypically contains information on:

-   -   The physical resource(s) on which the data is transmitted (e.g.        subcarriers or subcarrier blocks in case of OFDM, codes in case        of CDMA). This information allows the UE (receiver) to identify        the resources on which the data is transmitted.    -   When user equipment is configured to have a Carrier Indication        Field (CIF) in the L1/L2 control signaling this information        identifies the component carrier for which the specific control        signaling information is intended. This enables assignments to        be sent on one component carrier which are intended for another        component carrier (“cross-carrier scheduling”). This other,        cross-scheduled component carrier could be for example a        PDCCH-less component carrier, i.e. the cross-scheduled component        carrier does not carry any L1/L2 control signaling.    -   The Transport Format, which is used for the transmission. This        can be the transport block size of the data (payload size,        information bits size), the MCS (Modulation and Coding Scheme)        level, the Spectral Efficiency, the code rate, etc. This        information (usually together with the resource allocation (e.g.        the number of resource blocks assigned to the user equipment))        allows the user equipment (receiver) to identify the information        bit size, the modulation scheme and the code rate in order to        start the demodulation, the de-rate-matching and the decoding        process. The modulation scheme may be signaled explicitly.    -   Hybrid ARQ (HARQ) information:        -   HARQ process number: Allows the user equipment to identify            the hybrid ARQ process on which the data is mapped.        -   Sequence number or new data indicator (NDI): Allows the user            equipment to identify if the transmission is a new packet or            a retransmitted packet. If soft combining is implemented in            the HARQ protocol, the sequence number or new data indicator            together with the HARQ process number enables soft-combining            of the transmissions for a PDU prior to decoding.        -   Redundancy and/or constellation version: Tells the user            equipment, which hybrid ARQ redundancy version is used            (required for de-rate-matching) and/or which modulation            constellation version is used (required for demodulation).    -   UE Identity (UE ID): Tells for which user equipment the L1/L2        control signaling is intended for. In typical implementations        this information is used to mask the CRC of the L1/L2 control        signaling in order to prevent other user equipments to read this        information.

To enable an uplink packet data transmission, L1/L2 control signaling istransmitted on the downlink (PDCCH) to tell the user equipment about thetransmission details. This L1/L2 control signaling typically containsinformation on:

-   -   The physical resource(s) on which the user equipment should        transmit the data (e.g. subcarriers or subcarrier blocks in case        of OFDM, codes in case of CDMA).    -   When user equipment is configured to have a Carrier Indication        Field (CIF) in the L1/L2 control signaling this information        identifies the component carrier for which the specific control        signaling information is intended. This enables assignments to        be sent on one component carrier which are intended for another        component carrier. This other, cross-scheduled component carrier        may be for example a PDCCH-less component carrier, i.e. the        cross-scheduled component carrier does not carry any L1/L2        control signaling.    -   L1/L2 control signaling for uplink grants is sent on the DL        component carrier that is linked with the uplink component        carrier or on one of the several DL component carriers, if        several DL component carriers link to the same UL component        carrier.    -   The Transport Format, the user equipment should use for the        transmission. This can be the transport block size of the data        (payload size, information bits size), the MCS (Modulation and        Coding Scheme) level, the Spectral Efficiency, the code rate,        etc.

This information (usually together with the resource allocation (e.g.the number of resource blocks assigned to the user equipment)) allowsthe user equipment (transmitter) to pick the information bit size, themodulation scheme and the code rate in order to start the modulation,the rate-matching and the encoding process. In some cases the modulationscheme maybe signaled explicitly.

-   -   Hybrid ARQ information:        -   HARQ Process number: Tells the user equipment from which            hybrid ARQ process it should pick the data.        -   Sequence number or new data indicator: Tells the user            equipment to transmit a new packet or to retransmit a            packet. If soft combining is implemented in the HARQ            protocol, the sequence number or new data indicator together            with the HARQ process number enables soft-combining of the            transmissions for a protocol data unit (PDU) prior to            decoding.        -   Redundancy and/or constellation version: Tells the user            equipment, which hybrid ARQ redundancy version to use            (required for rate-matching) and/or which modulation            constellation version to use (required for modulation).    -   UE Identity (UE ID): Tells which user equipment should transmit        data. In typical implementations this information is used to        mask the CRC of the L1/L2 control signaling in order to prevent        other user equipments to read this information.

There are several different flavors how to exactly transmit theinformation pieces mentioned above in uplink and downlink datatransmission. Moreover, in uplink and downlink, the L1/L2 controlinformation may also contain additional information or may omit some ofthe information. For example:

-   -   HARQ process number may not be needed, i.e. is not signaled, in        case of a synchronous HARQ protocol.    -   A redundancy and/or constellation version may not be needed, and        thus not signaled, if Chase Combining is used (always the same        redundancy and/or constellation version) or if the sequence of        redundancy and/or constellation versions is pre-defined.    -   Power control information may be additionally included in the        control signaling.    -   MIMO related control information, such as e.g. pre-coding, may        be additionally included in the control signaling.    -   In case of multi-codeword MIMO transmission transport format        and/or HARQ information for multiple code words may be included.

For uplink resource assignments (on the Physical Uplink Shared Channel(PUSCH)) signaled on PDCCH in LTE, the L1/L2 control information doesnot contain a HARQ process number, since a synchronous HARQ protocol isemployed for LTE uplink. The HARQ process to be used for an uplinktransmission is given by the timing. Furthermore it should be noted thatthe redundancy version (RV) information is jointly encoded with thetransport format information, i.e. the RV info is embedded in thetransport format (TF) field. The Transport Format (TF) respectivelymodulation and coding scheme (MCS) field has for example a size of 5bits, which corresponds to 32 entries. 3 TF/MCS table entries arereserved for indicating redundancy versions (RVs) 1, 2 or 3. Theremaining MCS table entries are used to signal the MCS level (TBS)implicitly indicating RVO. The size of the CRC field of the PDCCH is 16bits.

For downlink assignments (PDSCH) signaled on PDCCH in LTE the RedundancyVersion (RV) is signaled separately in a two-bit field. Furthermore themodulation order information is jointly encoded with the transportformat information. Similar to the uplink case there is 5 bit MCS fieldsignaled on PDCCH. 3 of the entries are reserved to signal an explicitmodulation order, providing no Transport format (Transport block) info.For the remaining 29 entries modulation order and Transport block sizeinfo are signaled.

Physical Downlink Control Channel (PDCCH)

The physical downlink control channel (PDCCH) carries the L1/L2 controlsignaling, i.e. transmit power control commands and the schedulinggrants for allocating resources for downlink or uplink datatransmission. To be more precise, the downlink control channelinformation (i.e. the DCI contents, respectively, the L1/L2 controlsignaling information) is mapped to its corresponding physical channel,the PDCCH. This “mapping” includes the determination of a CRC attachmentfor the downlink control channel information, which is a CRC calculatedon the downlink control channel information being masked with an RNTI,as will explained below in more detail. The downlink control channelinformation and its CRC attachment are then transmitted on the PDCCH(see 3GPP TS 36.212, sections 4.2 and 5.3.3).

Each scheduling grant is defined based on Control Channel Elements(CCEs). Each CCE corresponds to a set of Resource Elements (REs). In3GPP LTE, one CCE consists of 9 Resource Element Groups (REGs), whereone REG consists of four REs.

The PDCCH is transmitted on the first one to three OFDM symbols within asub-frame. For a downlink grant on the physical downlink shared channel(PDSCH), the PDCCH assigns a PDSCH resource for (user) data within thesame sub-frame. The PDCCH control channel region within a sub-frameconsists of a set of CCE where the total number of CCEs in the controlregion of sub-frame is distributed throughout time and frequency controlresource. Multiple CCEs can be combined to effectively reduce the codingrate of the control channel. CCEs are combined in a predetermined mannerusing a tree structure to achieve different coding rate.

In 3GPP LTE (Release 8/9), a PDCCH can aggregate 1, 2, 4 or 8 CCEs. Thenumber of CCEs available for control channel assignment is a function ofseveral factors, including carrier bandwidth, number of transmitantennas, number of OFDM symbols used for control and the CCE size, etc.Multiple PDCCHs can be transmitted in a sub-frame.

Downlink control channel information in form of DCI transports downlinkor uplink scheduling information, requests for aperiodic CQI reports, oruplink power control commands for one RNTI (Radio Network TerminalIdentifier). The RNTI is a unique identifier commonly used in 3GPPsystems like 3GPP LTE (Release 8/9) for destining data or information toa specific user equipment. The RNTI is implicitly included in the PDCCHby masking a CRC calculated on the DCI with the RNTI—the result of thisoperation is the CRC attachment mentioned above. On the user equipmentside, if decoding of the payload size of data is successful, the userequipment detects the DCI to be destined to the user equipment bychecking whether the CRC on the decoded payload data using the“unmasked” CRC (i.e. after removing the masking using the RNTI) issuccessful. The masking of the CRC code is for example performed byscrambling the CRC with the RNTI.

In 3GPP LTE (Release 8) the following different DCI formats are defined:

Uplink DCI Formats:

-   -   Format 0 used for transmission of UL SCH assignments    -   Format 3 is used for transmission of TPC commands for PUCCH and        PUSCH with 2 bit power adjustments (multiple UEs are addressed)    -   Format 3A is used for transmission of TPC commands for PUCCH and

PUSCH with single bit power adjustments (multiple UEs are addressed)

Downlink DCI Formats:

-   -   Format 1 used for transmission of DL SCH assignments for SIMO        operation    -   Format 1A used for compact transmission of DL SCH assignments        for SIMO operation    -   Format 1B used to support closed loop single rank transmission        with possibly contiguous resource allocation    -   Format 1C is for downlink transmission of paging, RACH response        and dynamic BCCH scheduling    -   Format 1D is used for compact scheduling of one PDSCH codeword        with precoding and power offset information    -   Format 2 is used for transmission of DL-SCH assignments for        closed-loop MIMO operation    -   Format 2A is used for transmission of DL-SCH assignments for        open-loop MIMO operation

For further information on the LTE physical channel structure indownlink and the PDSCH and PDCCH format, see Stefania Sesia et al.,“LTE—The UMTS Long Term Evolution”, Wiley & Sons Ltd., ISBN978-0-47069716-0, April 2009, sections 6 and 9.

Blind Decoding of PDCCHs at the User Equipment

In 3GPP LTE (Release 8/9), the user equipment attempts to detect the DCIwithin the PDCCH using so-called “blind decoding” (sometimes alsoreferred to as “blind detection”). This means that there is noassociated control signaling that would indicate the CCE aggregationsize or modulation and coding scheme for the PDCCHs signaled in thedownlink, but the user equipment tests for all possible combinations ofCCE aggregation sizes and modulation and coding schemes, and confirmsthat successful decoding of a PDCCH based on the RNTI. To further limitcomplexity a common and dedicated search space in the control signalingregion of the LTE component carrier is defined in which the userequipment searches for PDCCHs.

In 3GPP LTE (Release 8/9) the PDCCH payload size is detected in oneblind decoding attempt. The user equipment attempts to decode twodifferent payload sizes for any configured transmission mode, ashighlighted in Table 1 below. Table 1 shows that payload size X of DCIformats 0,1A, 3, and 3A is identical irrespective of the transmissionmode configuration. The payload size of the other DCI format depends onthe transmission mode.

TABLE 1 DCI Formats payload size transmission payload size X differentfrom X mode 0/1A/3/3A 1C broadcast/unicast/ paging/power control 1 Mode1 DL TX modes 1 Mode 2 2A Mode 3 2 Mode 4 1B Mode 5 1D Mode 6 1 Mode 7 1Mode 1 SPS-Modes 1 Mode 2 2A Mode 3 2 Mode 4 1 Mode 7

Accordingly, the user equipment can check in a first blind decodingattempt the payload size of the DCI. Furthermore, the user equipment isfurther configured to only search for a given subset of the DCI formatsin order to avoid too high processing demands.

Medium Access Layer (MAC)

The MAC layer is one of the sub-layers of the the Layer 2 in the 3GPPLTE radio protocol stack. The MAC layer performs (de)multiplexingbetween logical channels and transport channels by (de)constructing MACPDUs (Protocol Data Units), also known as transport blocks. MAC PDUs areconstructed out of MAC SDUs (Service Data Units) received through one ormore logical channels in the transmitter. On the receiver side the MACPDUs are reconstructed out of the received MAC PDUs.

The transport block (MAC PDU) consists of a header and a payload. Apartfrom MAC SDUs the payload can consist of MAC Control Elements andpadding.

MAC Control Elements

For peer to peer signaling on MAC level MAC Control Elements (CEs) areused. MAC Control Elements can be part of a MAC PDU's payload asdescribed above and are identified by a specific Logical Channel ID(LCID) in the MAC header.

There are several types of MAC CEs. Some of them are only included inuplink transport blocks for signaling from user equipment to eNodeB,others only in downlink transport blocks for signaling from eNodeB touser equipment. The special LCIDs and the corresponding MAC ControlElements transmitted on the downlink are listed in Table 2.

TABLE 2 LCID value MAC Control Element used for 11100 UE ContentionResolution Identity 11101 Timing Advance Command 11110 DRX Command

The special LCIDs and the corresponding MAC Control Elements transmittedon the uplink are listed in Table 3.

TABLE 3 LCID value MAC Control Element used for 11010 Power HeadroomReport 11011 C-RNTI 11100 Truncated Buffer Status Report (BSR) 11101Short BSR 11110 Long BSR

Sounding Reference Signals (SRS)

Sounding reference signals are send in the uplink. Together with theDemodulation Reference Signals (DM RS) they are included in the uplinkto enable channel estimation for coherent demodulation as well aschannel quality estimation for uplink scheduling.

While DM RSs are associated with the transmission of uplink data, theSRSs are not associated with data transmission and primarily used forchannel quality estimation to enable frequency-selective scheduling bythe scheduling eNodeB. Furthermore SRSs can be used to enhance powercontrol or to support the eNodeB in deciding on initial Modulation andCoding Scheme (MCS) for data transmission. If configured by higher layersignaling, the SRSs are transmitted in the last SC-FDMA symbol in auplink sub-frame. The sub-frame in which SRSs are to be transmitted bythe user equipment is indicated by cell-specific broadcast signaling andis selected out of a set of 15 possible sub-frames within a radio frame.Data transmission on the Physical Uplink Shared CHannel (PUSCH) is notallowed in the sub-frame designated for transmitting SRSs, which setsthe SRS overhead to 7% when all possible sub-frames are configured forSRS transmission. As mentioned above, SRS configuration is done by theeNodeB using higher layer signaling. The configuration inter aliadetermines amongst other parameters duration and periodicity of theSRSs.

Further Advancements for LTE (LTE-A)

The frequency spectrum for IMT-Advanced was decided at the WorldRadiocommunication Conference 2007 (WRC-07). Although the overallfrequency spectrum for IMT-Advanced was decided, the actual availablefrequency bandwidth is different according to each region or country.Following the decision on the available frequency spectrum outline,however, standardization of a radio interface started in the 3rdGeneration Partnership Project (3GPP). At the 3GPP TSG RAN #39 meeting,the Study Item description on “Further Advancements for E-UTRA(LTE-Advanced)” was approved in the 3GPP. The study item coverstechnology components to be considered for the evolution of E-UTRA, e.g.to fulfill the requirements on IMT-Advanced. Two major technologycomponents which are currently under consideration for LTE-A aredescribed in the following.

Carrier Aggregation in LTE-A for Support of Wider Bandwidth

In Carrier Aggregation (CA), two or more Component Carriers (CCs) areaggregated in order to support wider transmission bandwidths up to 100MHz. All component carriers can be configured to be 3GPP LTE (Release8/9) compatible, at least when the aggregated numbers of componentcarriers in the uplink and the downlink are the same. This does notnecessarily mean that all component carriers need to be compatible to3GPP LTE (Release 8/9).

A user equipment may simultaneously receive or transmit on one ormultiple component carriers. On how many component carriers simultaneousreception/transmission is possible, is depending on the capabilities ofa user equipment.

A 3GPP LTE (Release 8/9) compatible user equipment can receive andtransmit on a single CC only, provided that the structure of the CCfollows the 3GPP LTE (Release 8/9) specifications, while a 3GPP LTE-A(Release 10) compatible user equipment with reception and/ortransmission capabilities for carrier aggregation can simultaneouslyreceive and/or transmit on multiple component carriers.

Carrier aggregation is supported for both contiguous and non-contiguouscomponent carriers with each component carrier limited to a maximum of110 Resource Blocks in the frequency domain using the 3GPP LTE (Release8/9) numerology.

It is possible to configure a 3GPP LTE-A (Release 10) compatible userequipment to aggregate a different number of component carriersoriginating from the same eNodeB (base station) and of possiblydifferent bandwidths in the uplink and the downlink. In a typical TDDdeployment, the number of component carriers and the bandwidth of eachcomponent carrier in uplink and downlink is the same. Component carriersoriginating from the same eNodeB need not to provide the same coverage.

The spacing between centre frequencies of contiguously aggregatedcomponent carriers shall be a multiple of 300 kHz. This is in order tobe compatible with the 100 kHz frequency raster of 3GPP LTE (Release8/9) and at the same time preserve orthogonality of the subcarriers with15 kHz spacing. Depending on the aggregation scenario, the n×300 kHzspacing can be facilitated by insertion of a low number of unusedsubcarriers between contiguous component carriers.

The nature of the aggregation of multiple carriers is only exposed up tothe MAC layer. For both uplink and downlink there is one HARQ entityrequired in MAC for each aggregated component carrier. There is (in theabsence of SU-MIMO for uplink) at most one transport block per componentcarrier. A transport block and its potential HARQ retransmissions needto be mapped on the same component carrier.

The Layer 2 structure with activated carrier aggregation is shown inFIG. 5 and FIG. 6 for the downlink and uplink respectively.

When carrier aggregation is configured, the user equipment only has oneRadio Resource Control (RRC) connection with the network. One cell—the“special cell”-provides the security input and the Non-Access Stratum(NAS) mobility information (e.g. TAI). There is only one special cellper user equipment in connected mode.

After RRC connection establishment to the special cell, thereconfiguration, addition and removal of component carriers can beperformed by RRC. At intra-LTE handover, RRC can also add, remove, orreconfigure component carriers for usage in the target cell. When addinga new component carrier, dedicated RRC signaling is used for sendingcomponent carriers' system information which is necessary for componentcarrier transmission/reception, similar to a handover in 3GPP LTE(Release 8/9).

When a user equipment is configured with carrier aggregation there isone pair of uplink and downlink component carriers that is alwaysactivate. The downlink component carrier of that pair might be alsoreferred to as ‘IX anchor carrier’. Same applies also for the uplink.

When carrier aggregation is configured, a user equipment may bescheduled over multiple component carriers simultaneously but at mostone random access procedure shall be ongoing at any time. Cross-carrierscheduling allows the PDCCH of a component carrier to schedule resourceson another component carrier. For this purpose a component carrieridentification field is introduced in the respective DCI formats.

A linking between uplink and downlink component carriers allowsidentifying the uplink component carrier for which the grant applieswhen there is no-cross-carrier scheduling.

The linkage of downlink component carriers to uplink component carriersdoes not necessarily need to be one to one. In other words, more thanone downlink component carrier can link to the same uplink componentcarrier. At the same time, a downlink component carrier can only link toone uplink component carrier. FIG. 7 and FIG. 8 exemplarily showpossible linkages between downlink and uplink component carriers. Whilein FIG. 7 all downlink component carriers are linked to the same uplinkcomponent carrier, in FIG. 8 downlink component carriers 1 and 2 arelinked to uplink component carrier 1 and downlink component carrier 3 islinked to uplink component carrier 2.

DRX and Carrier Aggregation

In order to provide reasonable battery consumption of user equipment3GPP LTE (Release 8/9) as well as 3GPP LTE-A (Release 10) provides aconcept of discontinuous reception (DRX).

For this concept the following terms describe the user equipment's statein terms of DRX.

-   -   on-duration: duration in downlink sub-frames that the user        equipment waits for, after waking up from DRX, to receive        PDCCHs. If the user equipment successfully decodes a PDCCH, the        user equipment stays awake and starts the inactivity timer;    -   inactivity-timer: duration in downlink sub-frames that the user        equipment waits to successfully decode a PDCCH, from the last        successful decoding of a PDCCH, failing which it re-enters DRX.        The user equipment shall restart the inactivity timer following        a single successful decoding of a PDCCH for a first transmission        only (i.e. not for retransmissions).    -   active-time: total duration that the user equipment is awake.        This includes the “on-duration” of the DRX cycle, the time user        equipment is performing continuous reception while the        inactivity timer has not expired and the time user equipment is        performing continuous reception while waiting for a downlink        retransmission after one HARQ RTT (Round Trip Time). Based on        the above the minimum active time is of length equal to        on-duration, and the maximum is undefined (infinite);

There is only one DRX cycle per user equipment. All aggregated componentcarriers follow this DRX pattern.

In order to allow for further battery saving optimization, a furtherstep of activation/deactivation of component carriers is introduced.Essentially a downlink component carrier could be in one of thefollowing three states: non-configured, configured but deactivated andactive. When a downlink component carrier is configured but deactivated,the user equipment does not need to receive the corresponding PDCCH orPDSCH, nor is it required to perform CQI measurements. Conversely, whena downlink component carrier is active, the user equipment shall receivePDSCH and PDCCH (if present), and is expected to be able to perform CQImeasurements. After configuration of component carriers in order to havePDCCH and PDSCH reception on a downlink component as described above,the downlink component carrier needs to be transitioned from configuredbut deactivated to active state.

In the uplink however, a user equipment is always required to be able totransmit on PUSCH on any configured uplink component carrier whenscheduled on the corresponding PDCCH (i.e. there is no explicitactivation of uplink component carriers).

For user equipment power-saving purposes, it's crucial that additionalcomponent carriers can be de-activated and activated in an efficient andfast way. With bursty data-transmission, it is imperative thatadditional component carriers can be activated and de-activated quickly,such that both the gains of high bit-rates can be utilized, and batterypreservation can be supported. As described before user equipments willnot perform and report CQI measurements on configured but deactivateddownlink component carriers but only radio resource management relatedmeasurements like RSRP (Reference Signal Received Power) and RSRQ(Reference Signal Received Quality) measurements. Hence when activatinga downlink component carrier, it's important that eNodeB acquiresquickly CQI information for the newly activated component carrier(s) inorder to being able to select an appropriate MCS for efficient downlinkscheduling. Without CQI information eNodeB doesn't have knowledge aboutuser equipment's downlink channel state and might only select a ratherconservative MCS for downlink data transmission which would in turn leadto some resource utilization inefficiency.

In order to acquire CQI information quickly, eNodeB can schedule anaperiodic CQI by means of an uplink scheduling grant. The aperiodic CQIwould be transmitted on the physical uplink shared channel (PUSCH).Therefore in order to activate a configured downlink component carrier,eNodeB would need to issue essentially two grants (PDCCH) to the UE, onedownlink PDCCH in order to indicate the activation of a downlinkcomponent carrier and one uplink PDCCH which schedules uplink resourcesfor the transmission of the aperiodic CQI. Furthermore both PDCCH has tobe sent respectively received in the same TTI in order to ensure, thatuser equipment measures and reports CQI information for the correctdownlink component carrier, i.e. the downlink component carrier whichwill be activated.

The correct reception of the aperiodic CQI can serve as anacknowledgement for the downlink activation command, i.e. when aperiodicCQI has been received eNodeB assumes that user equipment has activatedthe downlink component carrier indicated in the downlink PDCCH.

As it becomes apparent, the main drawback of the above describedcomponent carrier activation method is, that two PDCCHs are required inorder to activate a downlink component carrier. Furthermore due to thefact that the two PDCCHs need to be received/sent simultaneously,certain error cases may occur in the presence of PDCCH loss.

In case only the downlink “activation” PDCCH is lost, user equipmentwill not activate the downlink component carrier. However based onreceived CQI information eNB erroneously assumes downlink activation hassucceeded.

In the second error case when only the uplink PDCCH which requests theaperiodic CQI is lost, eNodeB doesn't acquire CQI and erroneouslyassumes that downlink activation has failed.

SUMMARY OF THE INVENTION

One object of the invention is to overcome at least one of the describedproblems. Furthermore, it is another object of the invention to enableefficient and robust (de)activation of component carriers.

The object is solved by the subject matter of the independent claims.Advantageous embodiments of the invention are subject to the dependentclaims.

A first aspect of the invention is the provision of a signaling formatfor communicating a component carrier (de)activation message forcontrolling the activation state of at least one component carrier. Theproposed format comprises an identifier of the intended recipient of thecomponent carrier (de)activation message, e.g. by including a mobileterminal identifier (ID). This mobile terminal ID (also referred to as aUE ID) may be for example explicitly signaled in a field of thecomponent carrier (de)activation message. In view of the componentcarrier (de)activation message indicating the intended recipient for thecomponent carrier (de)activation message, a CRC that is calculated basedon the component carrier (de)activation message can be scrambled with acomponent carrier-specific or cell-specific radio network temporaryidentifier. As will be outlined below in further detail, this has theadvantage that not as many radio network temporary identifiers (thetotal number of which is limited by the number of bits spent for theradio network temporary identifier) in comparison to a solution, where aradio network temporary identifier for component carrier (de)activationis assigned to the mobile terminals on a per-mobile terminal basis.

Furthermore, the component carrier (de)activation message format may beconsidered a new format of downlink control channel information that ismapped to the physical downlink control channel (PDCCH). The use of thecomponent carrier-specific or cell-specific radio network temporaryidentifiers therefore indicate the format of the downlink controlchannel information being a component carrier (de)activation message.Furthermore, in case of using component carrier-specific radio networktemporary identifier(s) that is/are linked to a respective componentcarrier, carrier-specific radio network temporary identifier(s) alsoindicate(s) a component carrier to be activated or deactivated. Hence,the component carrier (de)activation message as well as the CRCattachment (i.e. the CRC for the component carrier (de)activationmessage scrambled with a given radio network temporary identifier)indicate to the mobile terminal the activation state of the componentcarriers, i.e. indicate which of them is/are to be (de)activated.

Another, second of the invention is to propose a mechanism for(de)activating downlink component carriers configured by a mobileterminal by means of a component carrier (de)activation message that istransmitted on a physical downlink shared channel as part of a transportblock. According to this aspect of the invention, the component carrier(de)activation message comprises (de)activation information thatindicates for the respective downlink component carriers configured bythe mobile terminal, the activation state of the respective componentcarriers. This way, the mobile terminal can recognize a change in theactivation state of the respective downlink component carriers and mayactivate or deactivate them accordingly. In one exemplaryimplementation, the (de)activation information for the componentcarriers may be provided in a MAC control element, i.e. by means of MACsignaling.

Furthermore, still in line with this second aspect of the invention, the(de)activation information may be provided in form of a bitmap, theindividual bits of which indicate the activation state of a respectiveconfigured downlink component carrier associated to a respective bit ofthe bitmap.

It should be noted that—in line with the first and second aspect of theinvention—in cases where there is a downlink component carrierconfigured for the mobile terminal that is always active, the(de)activation information does not need to indicate the activationstate for such “always active” component carrier—the “always active”downlink component carrier is also referred to as the downlink primarycomponent carrier (PCC) herein.

A further aspect of the invention is to trigger the signaling ofsounding reference signals (SRSs) in the uplink. For this purpose, a SRS(de)activation message is defined which is reusing the differentstructures and mechanisms for transmitting the component carrier(de)activation message according to the various embodiments describedherein. For example, the SRS (de)activation message may also compriseSRS (de)activation information that indicated the activation state ofthe SRS transmission for the uplink component carriers configured forthe mobile terminal. This SRS (de)activation information may be providedin form of a bitmap, the individual bits of which indicate theactivation state SRS signaling on the respective configured uplinkcomponent carrier associated to a respective bit of the bitmap. Pleasenote that alternatively the bits of the bitmap in the SRS (de)activationmessage may also be considered associated to respective configureddownlink component carriers, and the logical values of the individualbits of the bitmap indicate the activation state of SRS signaling on theuplink component carrier linked to the respective downlink componentcarrier associated to the given bit in the bitmap. The SRS(de)activation message may be signaled as part of a transport block onthe physical uplink shared channel or may be signaled as a new format ofdownlink control channel information that is mapped to the physicaldownlink control channel (PDCCH) as described herein in line with thefirst aspect of the invention.

Moreover, the SRS (de)activation information may also be sent togetherwith (de)activation information for activating/deactivating configureddownlink component carriers within a single message. For example, theSRS (de)activation information and the component carrier (de)activationinformation may be signaled in a single MAC control element as part of atransport block of the physical downlink shared channel, or may besignaled together in a new format of downlink control channelinformation that is mapped to the physical downlink control channel(PDCCH) as described herein in line with the first aspect of theinvention.

According to one exemplary embodiment of the invention, a method for(de)activating configured component carriers in communication systemusing component carrier aggregation is provided. According to thismethod a mobile terminal receives on a physical downlink shared channela transport block comprising a component carrier (de)activation message.Component carrier (de)activation message comprises (de)activationinformation in form of a bitmap consisting of a number of bits. Each ofthe bits of the bitmap is associated to a respective one of theconfigured downlink component carriers, wherein logical value of eachbit is indicating whether the associated downlink component carrier isto be activated or deactivated. Furthermore, the mobile terminalactivates or deactivates the configured component carriers according to(de)activation information obtained from the component carrier(de)activation message.

In one exemplary implementation according to another embodiment of theinvention, the component carrier (de)activation message is a MAC controlelement.

Optionally, the component carrier (de)activation message may bemultiplexed to the transport block together with other logical channeldata to be transmitted to the mobile terminal.

In another embodiment of the invention, one of the plurality ofconfigured downlink component carriers is a downlink primary componentcarrier. This which primary component carrier cannot be activated ordeactivated by the component carrier (de)activation message.Accordingly, the (de)activation information of the component carrier(de)activation message do not need to comprise an indication of theactivation state of the primary component carrier of the mobileterminal.

In one exemplary implementation, the base station may ensure that thetransport block comprising a component carrier (de)activation message isreceived by the mobile terminal on the downlink primary componentcarrier of the mobile terminal.

Optionally, the component carrier (de)activation message may furthercomprise SRS information allowing the base station to request the mobileterminal to start sending a sounding reference signal (SRS) on at leastone of the uplink component carriers respectively linked to theconfigured downlink component carriers. In a more detailedimplementation, the SRS information is provided in form of a bitmapconsisting of a number of bits. Each of the bits of the bitmap withinthe SRS information is associated to a respective one of uplinkcomponent carriers and the logical value of each bit of the bitmap isindicating whether SRS should be transmitted on the associated uplinkcomponent carrier by the mobile terminal.

Another embodiment of the invention is providing a method for(de)activating configured component carriers in communication systemusing component carrier aggregation. According to this method the mobileterminal receives a sub-frame from a base station, and performs a blinddecoding within a control signaling region on one of the configureddownlink component carriers within the received sub-frame to obtain acomponent carrier (de)activation message and a CRC attachment thereof.The component carrier (de)activation message and its CRC attachment maybe considered a PDCCH. The CRC attachment comprises a CRC of thecomponent carrier (de)activation message, wherein the CRC is scrambledwith a component carrier-specific or cell-specific radio networktemporary identifier (RNTI) used for signaling the activation state ofthe target component carrier(s).

The mobile terminal checks the CRC of the CRC attachment using thecomponent carrier-specific or radio cell-specific radio networktemporary identifier. This may be for example realized by the mobileterminal descrambling the CRC with the component carrier-specific orradio cell-specific radio network temporary identifier, and subsequentlycomparing the resultant descrambled CRC with the locally generated CRCfrom the received and decoded downlink control channel information(without CRC).

In case of a match, i.e. if the CRC check passes, the mobile terminaldetermines a mobile terminal identifier (e.g. a UE ID or a mobileterminal-specific RNTI) from the component carrier (de)activationmessage. Based on the mobile terminal identifier the mobile terminalverifies whether the component carrier (de)activation message isdestined to the mobile terminal. If the component carrier (de)activationmessage is destined to the mobile terminal, the mobile terminalactivates or deactivates the configured component carriers according to(de)activation information obtained from the component carrier(de)activation message and/or implicit to the use of the radio networktemporary identifier for scrambling the CRC attachment.

Furthermore, according to another embodiment of the invention, anothermethod for (de)activating configured component carriers in communicationsystem using component carrier aggregation is employed. According tothis method the base station transmits a sub-frame to the mobileterminal. The sub-frame comprises within a control signaling region onone of the configured downlink component carriers a component carrier(de)activation message and a CRC attachment thereof (i.e. a PDCCH). Thecomponent carrier (de)activation message indicates at least a mobileterminal identifier to address the message to its intended receiver(mobile terminal). The CRC attachment comprises a CRC of the componentcarrier (de)activation message that has been calculated on the componentcarrier (de)activation message by a processor of the base station andhas been subsequently scrambled with a component carrier-specific orcell-specific radio network temporary identifier (RNTI) used forsignaling the activation state of the target component carrier(s).

In a further embodiment of the invention, the component carrier(de)activation message indicates which of the plurality of configureddownlink component carriers is/are to be activated, respectivelydeactivated. Hence, in this embodiment of the invention the indicationof the configured component carrier to be (de)activated may be comprisedin a carrier indication field of the component carrier (de)activationmessage.

Furthermore, in another exemplary embodiment, the state of the indicatedcomponent carrier is implicit to the RNTI used for scrambling the CRC.In this embodiment, there may be two radio cell-specific radio networktemporary identifiers used for signaling the activation state of thedownlink component carriers. One of the radio network temporaryidentifiers is indicating the activation of at least one of theconfigured downlink component carriers indicated in the componentcarrier (de)activation message and the other radio network temporaryidentifier is indicating the deactivation of at least one of theconfigured downlink component carriers indicated in the componentcarrier (de)activation message.

In an alternative implementation according to another embodiment of theinvention, the component carrier to be (de)activated is implicit to theRNTI used for scrambling the CRC. In this embodiment, it can be assumedthat each configured downlink component carrier is linked to a componentcarrier-specific radio network temporary identifier. The componentcarrier-specific radio network temporary identifier used for scramblingthe CRC thus implicitly indicates at least the configured downlinkcomponent carrier to be activated or deactivated.

In a variation of this embodiment, the component carrier (de)activationmessage indicates whether the configured downlink component carrier tobe activated or deactivated linked to the component carrier-specificradio network temporary identifier used for scrambling the CRC is to beactivated or deactivated.

In a further variation of this embodiment, each configured downlinkcomponent carrier may be linked to two component carrier-specific radionetwork temporary identifiers, and the component carrier-specific radionetwork temporary identifier used for scrambling the CRC indicates atleast the configured downlink component carrier and whether it is to beactivated or deactivated. Hence, in this variation the indication of thecomponent carrier and its activation state are implicit to the RNTI usedfor scrambling the CRC.

In another embodiment of the invention, the component carrier(de)activation message comprises an activation flag that requests themobile terminal to activate, respectively deactivate an indicatedconfigured downlink component carrier.

In one further exemplary embodiment, the component carrier(de)activation message received within the control signaling region of asub-frame is received on a downlink primary component carrier of themobile terminal.

In another embodiment of the invention, the activation of a downlinkcomponent carrier triggers the transmission of a power headroom reportby the mobile terminal for the uplink component carrier linked to thedownlink component carrier being activated. For example the mobileterminal may transmit, in response to the activation of a downlinkcomponent carrier, a power headroom report for the for the uplinkcomponent carrier linked to the downlink component carrier beingactivated. The power headroom report is transmitted by the mobileterminal on the linked uplink component carrier on resources assigned onthe linked uplink component carrier assigned to the mobile terminal bythe next uplink resource assignment for the linked uplink componentcarrier.

In a further embodiment of the invention, the mobile terminaldeactivates the indicated component carrier in case the componentcarrier (de)activation message indicates the deactivation of a downlinkcomponent carrier. This deactivation is however not performedimmediately, but

-   -   upon a HARQ protocol used for transmitting transport blocks is        acknowledging successful decoding of a transport block pending        for transmission on the downlink component carrier to be        deactivated at the time of receiving the component carrier        (de)activation message, or    -   upon reaching a maximum number of retransmissions of the HARQ        protocol for the transport block pending for transmission on the        downlink component carrier to be deactivated.

In this context the transport block pending for transmission isreferring to one or more transport blocks transmitted in individual HARQprocesses on the downlink component carrier to be deactivated and thatare currently transmitted (retransmission of the transporter block ispending) at the time of receiving the deactivation command for thedownlink component carrier.

In addition thereto, or alternatively, according to another embodimentof the invention, the component carrier (de)activation message comprisesa SRS flag that, when set, requests the mobile terminal to start sendinga sounding reference signal (SRS) on the uplink component carrier linkedto the indicated configured downlink component carrier. Optionally, theSRS flag, when not set, may request the mobile terminal to stop sendinga sounding reference signal (SRS) on the uplink component carrier linkedto the indicated configured downlink component carrier.

In addition to at least one of the activation flag and the SRS flag, oralternatively thereto, the component carrier (de)activation messageaccording to a further embodiment of the invention comprises a CQIrequest flag that, when set, requests channel quality feedback for theone or more indicated configured downlink component carriers.

In a variation of this embodiment, in case the mobile terminal isrequested to send channel quality feedback for an indicated downlinkcomponent carrier, the mobile terminal performs a channel qualitymeasurement for each downlink component carrier indicated by thecomponent carrier (de)activation message, and transmits the channelquality feedback for the one or more indicated downlink componentcarriers to the base station.

The channel quality feedback may be for example transmitted onpre-configured uplink resources on a physical uplink shared channel(PUSCH) or a physical uplink control channel (PUCCH), or alternativelyon uplink resources on the physical uplink control channel (PUCCH)configured by RRC for periodic channel quality feedback.

In one exemplary implementation the channel quality feedback istransmitted 4 sub-frames or 4 ms after having received the sub-framecomprising the component carrier (de)activation message.

In the examples given above, the channel quality feedback may be anaperiodic channel quality feedback. In addition or as an alternative totriggering such aperiodic channel quality feedback or alternativelythereto, the CQI flag may be used to trigger the mobile terminal tostart sending periodic channel quality feedback. Accordingly, in casethe mobile terminal is requested to send channel quality feedback for anindicated downlink component carrier the mobile terminal mayperiodically perform a channel quality measurement for each downlinkcomponent carrier indicated by the component carrier (de)activationmessage, and may periodically transmit the channel quality feedback forthe one or more indicated downlink component carriers to the basestation on uplink resources for example on the physical uplink controlchannel configured by RRC for periodic channel quality feedback.

Furthermore, in order not to increase the blind decoding attempts of themobile terminal to detect the format of the control channel informationsignaled on the PDCCH of the received sub-frame, in another embodimentof the invention, the component carrier (de)activation message format(which can be considered a DCI format) has the same size (number ofbits) as at least one other downlink control information format definedin the mobile communication system. For example, when implementing theinvention in a 3GPP LTE-A (Release 10) system or its successors, thecomponent carrier (de)activation message format may have the same sizeas DCI formats 0/1A in 3GPP LTE (Release 8/9) or 3GPP LTE-A (Release10). Moreover, the size of the component carrier (de)activation messageformat may optionally depend on the component carrier bandwidth. Thecomponent carrier bandwidth may be for example the bandwidth of thecomponent carrier the activation state of which is signaled by thecomponent carrier (de)activation message and/or its CRC attachment, orthe bandwidth of the component carrier on which the component carrier(de)activation message is signaled.

In another embodiment of the invention, the reception of the componentcarrier (de)activation message is acknowledged by the mobile terminal.This may be for example realized by signaling an ACK/NACK in the uplinkat a given timing relative to the transmission of the component carrier(de)activation message. Alternatively, the acknowledgment may also besent in form of channel quality feedback on the indicated downlinkcomponent carrier(s). This latter option may for example be useful, if aCQI flag in the component carrier (de)activation message is triggeringchannel quality feedback from the mobile terminal.

A further aspect of the invention is the implementation of the differentmethods for (de)activating configured component carriers incommunication system using component carrier aggregation in hardwareand/or software. In this respect, different apparatuses that perform orparticipate in the performance of such methods are provided.

One embodiment of the invention thus provides a mobile terminal for(de)activating configured component carriers in communication systemusing component carrier aggregation. The mobile terminal comprises areceiver for receiving on a physical downlink shared channel a transportblock comprising a component carrier (de)activation message, wherein thecomponent carrier (de)activation message comprises (de)activationinformation indicating which of a plurality of configured downlinkcomponent carriers is/are to be activated, respectively deactivated bythe mobile terminal, and a processor for activating or deactivating theconfigured component carriers according to (de)activation informationobtained from the component carrier (de)activation message.

Furthermore, according to an embodiment of the invention, the mobileterminal is adapted to/comprises means to perform the method for(de)activating configured component carriers in communication systemusing component carrier aggregation according to one of the variousembodiments described herein, where the component carrier (de)activationmessage is sent as part of a transport block on the physical downlinkshared channel.

Another embodiment of the invention provides a mobile terminal for usein a communication system using component carrier aggregation. Themobile terminal comprises a receiver for receiving a sub-frame from abase station, and a processing means for performing a blind decodingwithin a control signaling region on one of the configured downlinkcomponent carriers within the received sub-frame to obtain a componentcarrier (de)activation message and a CRC attachment thereof, wherein theCRC attachment comprises a CRC of the component carrier (de)activationmessage, the CRC being scrambled with a component carrier-specific orcell-specific radio network temporary identifier (RNTI) used forsignaling the activation state of the target component carrier(s). Theblind decoding may for example also involve the operations of a decoderand a demodulator of the mobile terminal.

The mobile terminal's processor further checks the CRC of the CRCattachment using the component carrier-specific or radio cell-specificradio network temporary identifier. As mentioned above, this check ofthe CRC may be for example implemented by descrambling the CRC of theCRC attachment using the component carrier-specific or radiocell-specific radio network temporary identifier, and subsequentlycomparing the descrambled CRC with the a CRC (locally) generated by theprocessor of the mobile terminal from the received and decoded downlinkcontrol channel.

In case of a match, i.e. in case the CRC check passes, the mobileterminal determines a mobile terminal identifier from the componentcarrier (de)activation message. Furthermore, the processor verifiesbased on the mobile terminal identifier whether the component carrier(de)activation message is destined to the mobile terminal. Accordingly,the mobile terminal can activate or deactivate the configured componentcarriers according to (de)activation information obtained from thecomponent carrier (de)activation message and/or implicit to the use ofthe radio network temporary identifier for scrambling the CRCattachment, if the component carrier (de)activation message is destinedto the mobile terminal.

In another embodiment of the invention, a base station for(de)activating configured component carriers of a mobile terminal incommunication system using component carrier aggregation is provided.The base station comprises a processor for generating a componentcarrier (de)activation message comprising at least a mobile terminalidentifier of the mobile terminal. The processor further determines aCRC for the component carrier (de)activation message, and scrambles theCRC with a component carrier-specific or cell-specific radio networktemporary identifier (RNTI) used for signaling the activation state ofthe target component carrier(s), to thereby obtain a CRC attachment ofthe component carrier (de)activation message. Moreover, the base stationalso includes a transmitter for transmitting the component carrier(de)activation message and its CRC attachment within the controlsignaling region of a downlink component carrier within a sub-frame tothe mobile terminal.

The invention further relates the implementation of the methods for(de)activating configured component carriers in communication systemusing component carrier aggregation described herein in software. Onefurther embodiment of the invention is therefore providing acomputer-readable medium storing instructions that, when executed by aprocessor of a mobile terminal, cause the mobile terminal to(de)activate configured component carriers in communication system usingcomponent carrier aggregation, by receiving on a physical downlinkshared channel a transport block comprising a component carrier(de)activation message, wherein the component carrier (de)activationmessage comprises (de)activation information indicating which of aplurality of configured downlink component carriers is/are to beactivated, respectively deactivated by the mobile terminal, andactivating or deactivating the configured component carriers accordingto (de)activation information obtained from the component carrier(de)activation message.

A further embodiment of the invention relates to a computer-readablemedium that is storing instructions that, when executed by a processorof a mobile terminal, cause the mobile terminal to perform one of thedifferent methods for (de)activating configured component carriers incommunication system using component carrier aggregation. In oneexample, the mobile terminal may be for example caused to receive asub-frame from a base station, and to perform a blind decoding within acontrol signaling region on one of the configured downlink componentcarriers within the received sub-frame to obtain a component carrier(de)activation message and a CRC attachment thereof. The CRC attachmentcomprises a CRC of the component carrier (de)activation message, whereinthe CRC is scrambled with a component carrier-specific or cell-specificradio network temporary identifier (RNTI) used for signaling theactivation state of the target component carrier(s).

The mobile terminal may be further caused by the executed instructionsto check the CRC of the CRC attachment using the componentcarrier-specific or radio cell-specific radio network temporaryidentifier. In case the CRC check passes, the mobile terminal is causedto determine a mobile terminal identifier (e.g. a UE ID or a mobileterminal-specific RNTI) from the component carrier (de)activationmessage. Moreover, the instructions, when executed by the mobileterminal's processor, cause the mobile terminal to verify based on themobile terminal identifier whether the component carrier (de)activationmessage is destined to the mobile terminal, and If the component carrier(de)activation message is destined to the mobile terminal, to activateor deactivates the configured component carriers according to(de)activation information obtained from the component carrier(de)activation message and/or implicit to the use of the radio networktemporary identifier for scrambling the CRC attachment.

Another embodiment therefore relates to a computer-readable medium thatis storing instructions that, when executed by a processor of a basestation, cause the base station to perform one of the different methodsfor (de)activating configured component carriers in communication systemusing component carrier aggregation. In one example, the base stationmay be for example caused to generate a component carrier (de)activationmessage comprising at least a mobile terminal identifier of the mobileterminal. The execution of the instructions by the processor of the basestation may further cause the base station to determine a CRC for thecomponent carrier (de)activation message, and to scramble the CRC with acomponent carrier-specific or cell-specific radio network temporaryidentifier (RNTI) used for signaling the activation state of the targetcomponent carrier(s), for thereby obtaining a CRC attachment of thecomponent carrier (de)activation message. Moreover, the base station isalso caused by the execution of the instructions by its processor totransmit the component carrier (de)activation message and its CRCattachment within the control signaling region of a downlink componentcarrier within a sub-frame to the mobile terminal.

BRIEF DESCRIPTION OF THE FIGURES

In the following the invention is described in more detail in referenceto the attached figures and drawings. Similar or corresponding detailsin the figures are marked with the same reference numerals.

FIG. 1 shows an exemplary architecture of a 3GPP LTE system,

FIG. 2 shows an exemplary overview of the overall E-UTRAN architectureof 3GPP LTE,

FIG. 3 shows an exemplary sub-frame structure on a downlink componentcarrier as defined for 3GPP LTE (Release 8/9),

FIG. 4 shows an exemplary downlink resource grid of a downlink slot asdefined for 3GPP LTE (Release 8/9),

FIGS. 5 & 6 show the 3GPP LTE-A (Release 10) Layer 2 structure withactivated carrier aggregation for the downlink and uplink, respectively,

FIGS. 7 & 8 show exemplarily linkages between downlink and uplinkcomponent carriers in 3GPP LTE-A (Release 10),

FIG. 9 exemplarily shows the dependence of the size of the componentcarrier (de)activation message from the bandwidth of a component carrieraccording to an embodiment of the invention and in relation to DCIformat 0/1A,

FIGS. 10 to 19 show different formats of the component carrier(de)activation message according to different embodiments of theinvention,

FIGS. 20 to 23 show different exemplary scenarios related toacknowledging the component carrier (de)activation message and thetriggering of CQI reporting from the mobile terminal in accordance withdifferent embodiments of the invention,

FIG. 24 shows a MAC control element according to an exemplary embodimentof the invention for simultaneously (de)activating one or more downlinkcomponent carriers and (de)activating SRS transmissions on one or more(linked) uplink component carriers of the user equipment, and

FIGS. 25 & 26 show different formats of the component carrier(de)activation message according to different embodiments of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The following paragraphs will describe various embodiments of theinvention. For exemplary purposes only, most of the embodiments areoutlined in relation to an orthogonal single-carrier uplink radio accessscheme according to 3GPP LTE (Release 8) and LTE-A (Release 10) mobilecommunication systems discussed in the Technical Background sectionabove. It should be noted that the invention may be advantageously usedfor example in connection with a mobile communication system such as3GPP LTE (Release 8) and LTE-A (Release 10) communication systemspreviously described, but the invention is not limited to its use inthis particular exemplary communication network.

The explanations given in the Technical Background section above areintended to better understand the mostly 3GPP LTE (Release 8) and LTE-A(Release 10) specific exemplary embodiments described herein and shouldnot be understood as limiting the invention to the described specificimplementations of processes and functions in the mobile communicationnetwork.

One possible implementation to indicate a component carrier in thedownlink that is to be activated is the use of the CIF field in thedownlink DCI formats of 3GPP LTE-A (Release 10). In case that the CIFfield points to a configured but deactivated downlink component carrier,this downlink component carrier is activated. However this approachcannot be used in a straightforward fashion to deactivate a componentcarrier. Furthermore, the CIF field may not be a mandatory part of theDCI formats.

Another solution for (de)activating configured downlink componentcarriers is to employ a mechanism similar to the 3GPP LTE (Release 8/9)semi-persistent scheduling (SPS) activation and deactivation. Each userequipment is assigned a UE-specific RNTI (SPS-C-RNTI). In case that theDCI CRC is scrambled with the SPS-C-RNTI, this DCI is interpreted asactivation or deactivation message. This mechanism could also be usedfrom the activation and deactivation of the downlink component carriers.However, this may have a drawback that for each user equipment for whicha carrier aggregation is configured, a new separate RNTI would berequired. As the total number of RNTIs is limited to 65536, many ofthese are required for non-carrier-aggregation purposes (e.g. C-RNTI,SPS-C-RNTI, etc) and the number of user equipments in carrier activationshould support a large peak number, it would be beneficial to find othermethods which do not impose such a requirement.

Another solution for (de)activating configured downlink componentcarriers and in line with a first aspect of the invention, a signalingformat for communicating a component carrier (de)activation message forcontrolling the activation state of at least one component carrier isprovided. The proposed new format of a component carrier (de)activationmessage allows for an explicit identification of the intended recipientof the component carrier (de)activation message. For example, thisidentification can be realized by including a mobile terminal identifier(ID) to the component carrier (de)activation message. This mobileterminal ID (also referred to as a UE ID) is for example signaled in amobile terminal identifier field of the component carrier (de)activationmessage. In one exemplary implementation the mobile terminal IDindicated in the component carrier (de)activation message is a mobileterminal-specific identifier, such as for example a C-RNTI of the mobileterminal.

In view of the component carrier (de)activation message indicating theintended recipient for the component carrier (de)activation message, itis not longer necessary to unambiguously identify the intended recipientof the component carrier (de)activation message by means of scramblingthe CRC of the component carrier (de)activation message with a mobileterminal-specific identifier. The component carrier (de)activationmessage format can be considered a downlink control information (DCI)format. In the physical layer, the component carrier (de)activationmessage is downlink control channel information that is mapped to thephysical downlink control channel (PDCCH) for transmission to the mobileterminal.

In line with the first aspect of the invention, a CRC is calculatedbased on the component carrier (de)activation message and is scrambledat the base station. The scrambling is performed at the base stationusing a component carrier-specific or cell-specific radio networktemporary identifier. As indicated above, this implies a significantlyreduced number of radio network temporary identifier(s) that need to bereserved for controlling the (de)activation state of the configuredcomponent carriers.

As mentioned in the previous paragraph, the component carrier(de)activation message format may be considered a new format of downlinkcontrol channel information that is mapped to the physical downlinkcontrol channel (PDCCH). The component carrier-specific or cell-specificradio network temporary identifier(s) used for scrambling the CRC of acomponent carrier (de)activation message thus indicate the format of thedownlink control channel information being a component carrier(de)activation message.

Furthermore, in case of using component carrier-specific radio networktemporary identifier(s) that is/are linked to a respective componentcarrier, carrier-specific radio network temporary identifier(s) alsoindicate(s) a component carrier to be activated or deactivated. Hence,the component carrier (de)activation message as well as the CRCattachment (i.e. the CRC for the component carrier (de)activationmessage scrambled with a given radio network temporary identifier)indicate to the mobile terminal the desired activation state of thecomponent carriers, i.e. indicate which of them is/are to be(de)activated.

A further solution for (de)activating configured downlink componentcarriers and in line with a second aspect of the invention, thecomponent carrier (de)activation message is provided within a transportblock in the physical downlink shared channel (PDSCH). The transportblock is thus transmitted as (part of) a scheduled transmission on thePDSCH to the mobile terminal. The component carrier (de)activationmessage may be multiplexed with other data of logical channels to thetransport block. Furthermore, the component carrier (de)activationmessage may be optionally assigned a logical channel identifier (LCID).

Similar to the solutions in line with the first aspect of the invention,the component carrier (de)activation message comprises (de)activationinformation that indicate for the respective downlink component carriersconfigured by the mobile terminal, the activation state of therespective component carriers and which allow the mobile terminalrecognize a change in the activation state of the respective downlinkcomponent carriers. The detection of such change of the activation statefor one or more downlink component carriers will cause the mobileterminal to activate or deactivate the effected configured downlinkcomponent carrier(s) accordingly. In one exemplary implementation, the(de)activation information for the component carriers may be provided ina MAC control element, i.e. by means of MAC signaling.

Furthermore, still in line with this second aspect of the invention, the(de)activation information may be provided in form of a bitmap. Theindividual bits of the bitmap indicate the activation state of arespective configured downlink component carrier associated to arespective bit of the bitmap.

A further aspect of the invention is to trigger the signaling ofsounding reference signals (SRSs) in the uplink. This may be done bymeans of an individual signaling message or together with the(de)activation of configured component carriers. In case of using anindividual signaling message, a SRS (de)activation message may bedefined. This SRS (de)activation message may reuse the differentstructures and mechanisms for transmitting the component carrier(de)activation message according to the various embodiments describedherein. For example, the SRS (de)activation message may comprise SRS(de)activation information that indicated the activation state of theSRS transmission for the uplink component carriers configured for themobile terminal.

This SRS (de)activation information may be structured similarly to thecomponent carrier (de)activation information. For example, the SRS(de)activation information may be provided in form of a bitmap. Theindividual bits of this bitmap may indicate the activation state SRSsignaling on the respective configured uplink component carrierassociated to a respective bit of the bitmap. Alternatively the bits ofthe bitmap in the SRS (de)activation message may also be consideredassociated to respective configured downlink component carriers, and thelogical values of the individual bits of the bitmap indicate theactivation state of SRS signaling on the uplink component carrier linkedto the respective downlink component carrier associated to the given bitin the bitmap.

The SRS (de)activation message may be signaled as part of a transportblock on the physical uplink shared channel as described herein in theembodiment in line with the second aspect of this invention) or may besignaled as a new format of downlink control channel information that ismapped to the physical downlink control channel (PDCCH) as describedherein in the embodiment in line with the first aspect of the invention.

Moreover, the SRS (de)activation information may also be sent togetherwith (de)activation information for activating/deactivating configureddownlink component carriers within a single message. In one exemplaryembodiment of the invention, the SRS (de)activation information and thecomponent carrier (de)activation information are signaled in a MACcontrol element as part of a transport block of the physical downlinkshared channel. In a further exemplary embodiment, the SRS(de)activation information and the component carrier (de)activationinformation are signaled together in a new format of downlink controlchannel information that is mapped to the physical downlink controlchannel (PDCCH) as described herein in line with the first aspect of theinvention. Please note that the principles for component carrier(de)activation may be applied for the activation and deactivation ofdownlink and uplink component carriers. In this respect it should befurther noted that it is assumed in the exemplary embodiments andimplementations of the invention, that a component carrier could bedefined to be in one of the following three activation states:non-configured, configured but deactivated and active. Moreover, it isalso important to notice that In cases where there is a downlink (and/oruplink) component carrier configured for the mobile terminal that isalways active, the(de)activation information does not need to indicatethe activation state for such “always active” component carrier—an“always active” component carrier is also referred to as the primarycomponent carrier (PCC) herein.

Exemplarily considering downlink component carriers, when a downlinkcomponent carrier is configured but deactivated, the user equipment doesnot need to receive the corresponding PDCCH or PDSCH, nor is it requiredto perform CQI measurements. Conversely, when a downlink componentcarrier is active, the user equipment shall receive PDSCH and PDCCH (ifpresent), and is expected to be able to perform CQI measurements. Afterconfiguration of component carrier(s) same is/are in configured butdeactivated state. In order to enable PDCCH and PDSCH reception on adownlink component carrier, the downlink component carrier needs to betransitioned from configured but deactivated state to active state. Theconfiguration of a component carrier may alternatively implicitly orexplicitly activate the component carrier, in which case the componentcarrier needs to be transitioned from active (“configured and active”)state to configured but deactivated state in order to save processingresources and/or signaling.

When an uplink component carrier is configured and activated, it isassumed to be eligible for transmission of signals and channels such asACK/NACK, sounding reference symbols, scheduling request, and periodicCQI reports. Conversely, when the downlink component carrier is inconfigured but deactivated state, the uplink component carrier isassumed to be completely muted and not eligible for transmission ofuplink signals and channels such as the above.

The new proposed component carrier (de)activation according to thevarious embodiments of the invention described herein may therefore beused for indicating state transitions between configured but deactivatedstate and active state (“configured and activated”).

As outlined above, one aspect of the invention is the proposal of a newcomponent carrier (de)activation message for (de)activating one or moreuplink or downlink component carriers. According to one embodiment ofthe invention related to the implementation of the concepts of thisinvention in a 3GPP based system using carrier aggregation in downlinkand/or uplink, the format for the new component carrier (de)activationmessage is a DCI format. The new component carrier (de)activationmessage contains at least a target UE ID, such as for example the C-RNTIof the user equipment to which the new component carrier (de)activationmessage is destined. Furthermore, in case the component carrier(s) towhich the new component carrier (de)activation message pertains is/arenot implicit to the RNTI used for scrambling the CRC of the newcomponent carrier (de)activation message, the new component carrier(de)activation message further contains a target component carrier ID.An example for a component carrier (de)activation message according toone embodiment of the invention including a CQI request flag is shown inFIG. 16. The remaining bits available in the component carrier(de)activation message may be used to signal further information orrequests to the mobile terminal as will be discussed below, or may befilled with padding or reserved bits.

This target component carrier ID may be for example signaled in a fieldof the new component carrier (de)activation message, which has a size of┌ log₂(N−1)┐ bits, given that there is one always-active componentcarrier in the downlink/uplink, the so-called anchor carrier, whichcannot be activated/deactivated by this message, and where N is thenumber of configured downlink/uplink component carriers and ┌x┐ is theceiling function, i.e. the smallest integer number that is larger thanor equal to x. Hence, for a typical downlink scenario, one can assumethat there are up to N=5 configured downlink component carriers, one ofthem being defined as the anchor carrier, so that a total of 2 bitswould be needed for the target component carrier ID in the componentcarrier (de)activation message.

Furthermore, according to a further aspect and embodiment of theinvention, no user equipment-specific RNTI is used to scramble the CRCfor the component carrier (de)activation message, when mapping thecomponent carrier (de)activation message as downlink control channelinformation to the PDCCH. This becomes possible since the target UE IDis part of the payload of the component carrier (de)activation message.Instead, the RNTI(s) used for signaling messages related to the(de)activation of component carriers, such as the component carrier(de)activation message, is either a cell-specific RNTI or a componentcarrier-specific RNTI.

If the scrambling of the CRC is using a single cell-specific RNTIdefined for the signaling of messages relates to the (de)activation ofcomponent carriers, such as the component carrier (de)activationmessage, the component carrier (de)activation message's payload furtherincludes information for which component carrier the (de)activationcommand should be applied. For this purpose, the component carrier(de)activation message may comprise one or more target component carrierIDs to indicate one or more component carriers in the downlink oruplink, which should be activated or deactivated. The base station mayindicate the cell-specific RNTI for component carrier (de)activation tothe mobile terminal by RRC signaling, e.g. as part of a componentcarrier configuration message.

In case the one or all component carriers indicated in the componentcarrier (de)activation message should be (simultaneously) activated ordeactivated, the component carrier (de)activation message may comprisean additional activation/deactivation flag to indicate whether the oneor more component carriers are to be activated or deactivated. Anotherexample for a component carrier (de)activation message according to afurther embodiment of the invention including multiple target componentcarrier IDs and a single activation/deactivation flag is shown in FIG.11.

In an alternative implementation according to a further embodiment, thecomponent carrier (de)activation message comprises anactivation/deactivation flag for each target component carrier IDindicated in the target component carrier IDs. This way, the basestation can control the mobile terminal to individually activate ordeactivate the respective component carrier(s) indicated by the targetcomponent carrier ID(s). Please note that it is a matter of definitionof whether the target component carrier ID and a correspondingactivation/deactivation flag is considered two fields of the componentcarrier (de)activation message or whether the two information isprovided in a single signaling component carrier activation/deactivationfield. An example for a component carrier (de)activation messageaccording to one embodiment of the invention including multiple targetcomponent carrier IDs and activation/deactivation flags is shown in FIG.12.

Furthermore, in another embodiment of the invention, there are twocell-specific RNTIs defined for the signaling of messages relates to the(de)activation of component carriers, such as the component carrier(de)activation message. In this case one of the two RNTIs (ActivationRNTI) can be used to indicate the activation of the component carrier(s)indicated by means of one or more target component carrier IDs in thecomponent carrier (de)activation message. Likewise, the other one of thetwo RNTIs (Deactivation RNTI) can be used to indicate the deactivationof the component carrier(s) indicated by means of one or more targetcomponent carrier IDs in the component carrier (de)activation message.Therefore, no additional activation/deactivation flag is needed in thepayload of the component carrier (de)activation message in thisexemplary implementation. The base station may indicate the ActivationRNTI and Deactivation RNTI for component carrier (de)activation andtheir respective function (activation/deactivation) to the mobileterminal by means of RRC signaling, e.g. as part of a component carrierconfiguration message. An example for a component carrier (de)activationmessage according to an embodiment of the invention including a targetcomponent carrier ID but no activation/deactivation flags is shown inFIG. 13.

In another embodiment of the invention, one or two cell-specific RNTIsmay be used as described above. Instead of indicating individualcomponent carrier to be activated by means of the target componentcarrier IDs (and using respective activation/deactivation flags), abit-mask is signaled in the component carrier (de)activation message toindicate the activation state of each configured downlink/uplinkcomponent carrier. An example for a component carrier (de)activationmessage for the (de)activation of downlink/uplink component carriers isshown in FIG. 18. The bit-mask is comprises in the CC bit-mask field.The bit-mask consists of N−1 bits, where N is the number of configureddownlink/uplink component carriers. If there are N=5 configuredcomponent carriers, the bit-mask has a size of 4 bits. Please note thatonly N−1 bits are required, if assuming that there is always one activedownlink component carrier in the uplink and downlink for a mobileterminal in connected mode. Each of the bits in the bit-mask is linkedto a corresponding configured component carrier in the downlink/uplink.The logical value 1 of a bit of the bit-mask may indicate the configureddownlink component carrier associated to the bit being active, while thelogical value 0 of a bit of the bit-mask may indicate the correspondingconfigured downlink component carrier associated to the bit beingconfigured but deactivated (or vice versa). The use of the(de)activation message according to this embodiment of the invention hasthe benefit that a single DCI payload can activate and deactivateseveral component carriers simultaneously.

The association between the respective association between the bits ofthe bit-mask (or the codepoints of the bit-maks field) and a componentcarrier may be for example configured for each mobile terminal a higherlayer, e.g. RRC, configuration message.

In accordance with a further embodiment of the invention a componentcarrier-specific RNTI is used for scrambling the CRC. In thisembodiment, each of the configured component carriers in the downlink oruplink is assigned a specific RNTI. The component carrier-specific RNTIsmay also be defined per-cell, so that they can be considered a sub-classof the cell-specific RNTIs. Please note that the anchor carrier may alsobe assigned a component carrier-specific RNTI, as different mobileterminals may have different anchor carriers in a cell controlled by abase station.

The mobile terminal may be informed by the base station on thecorrespondence of component carrier-RNTIs and component carriers. Thecorrespondence information may for example be signaled to the mobileterminal via RRC signaling, e.g. as part of the component carrierconfiguration message. One benefit of the use of componentcarrier-specific RNTI(s) is that a mobile node that is not configured tomonitor component carrier-specific RNTI(s) for the (de)activation ofcomponent carriers, cannot falsely (de)activate a component carrier incase of a corrupted DCI message. Furthermore, in addition to thecomponent carrier-specific RNTI(s) also the target UE ID in the(de)activation message has to match, so that a false (de)activation of acomponent carrier is less likely.

In this case, the component carrier-specific RNTI used by the basestation for scrambling the CRC of the component carrier (de)activationmessage already indicates to the mobile terminal the component carrierto which the (de)activation command of the component carrier(de)activation message pertains. Hence, the component carrier(de)activation message may not include a target component carrier ID inthis case. Nevertheless, the component carrier (de)activation messagemay still include the activation/deactivation flag to indicate theactivation state to be set for the component carrier indicated by thecomponent carrier-specific RNTI. An example for a component carrier(de)activation message according to an embodiment of the invention anactivation/deactivation flag for the downlink component carrier implicitto the component carrier-specific RNTI used for scrambling the CRC isshown in FIG. 14.

In another alternative embodiment, there are two componentscarrier-specific RNTIs defined for each component carrier for scramblingthe CRC of component carrier (de)activation related messages, such asthe proposed component carrier (de)activation message. Similar to theexample above, one of the two component carrier-specific RNTIs(Activation RNTI) is indicating to activate the component carrier linkedto the component carrier-specific RNTI, while the other one of the twocomponent carrier-specific RNTIs (Deactivation RNTI) is indicating todeactivate the component carrier linked to the componentcarrier-specific RNTI. This way, the component carrier (de)activationmessage may only need to signal the UE ID to destine the componentcarrier (de)activation related message to the correct recipient (userequipment), while the component carrier to be (de)activated is implicitto the use of the RNTI for scrambling the CRC of the component carrier(de)activation related message. Please note that also in this case thebase station may indicate the correspondence of Activation RNTIs andDeactivation RNTIs for the different component carriers by means of RRCsignaling, e.g. as part of a component carrier configuration message. Anexample for a component carrier (de)activation message according to anembodiment of the invention only comprising the target UE ID andoptionally further information and request (Extended Usage) is shown inFIG. 15.

Irrespective of whether (a) cell-specific or component carrier-specificRNTI(s) are used, these RNTIs may be signaled to the mobile terminals bymeans of RRC signaling or other means of sending control informationrelated to the carrier aggregation mode. In particular, when configuringthe terminal to which component carrier(s) it should consider as being“configured”, the mobile terminal is also notified which RNTI(s) to usefor one or more such configured component carriers.

Furthermore, in a 3GPP based communication system using OFDM on thedownlink, it can be assumed that the component carrier (de)activationmessage is forming the payload (DCI) of a PDCCH transmitted within asub-frame on a downlink component carrier to one or more user equipmentsand the user equipments perform a blind decoding on the different DCIformats signaled in a sub-frame on PDCCH. Using the same size as atleast one other DCI format defined in the communication system for thecomponent carrier (de)activation message format, and using an implicitthis format by means of the cell-specific or component carrier specificRNTI(s), it is possible not to increase the blind decoding efforts of amobile terminal.

As the format of the component carrier (de)activation message is thusassumed to have a given size, the remaining bits not needed to signalthe UE ID and the component carrier (de)activation related informationsuch as target component carrier ID(s) and activation flag(s) may be forexample used to signal further information or requests to the mobileterminals. Please note that in the different examples described aboveexplaining how cell-specific or component carrier specific RNTI(s) canbe used, some allow to avoid the signaling of target component carrierID(s) and/or activation/deactivation flag(s), so that the size of thecomponent carrier (de)activation related information may be minimized(or even avoided). Moreover, the size of the component carrier(de)activation message format may be either constant (fixed) or maydepend on the component carrier bandwidth, e.g. the bandwidth of the(de)activated component carrier, the bandwidth of the component carrierin the downlink on which the component carrier (de)activation message issignaled, or the linked uplink component carrier of the downlink onwhich the component carrier (de)activation message is signaled.

In one exemplary implementation, the size of the component carrier(de)activation message format is corresponding to the size of DCIformats 0/1A in 3GPP LTE (Release 8/9) or 3GPP LTE-A (Release 10). Theformat size may optionally depend on the component carrier bandwidth.

In this context, Table 4 illustrates the sizes of formats 0/1A in 3GPPLTE (Release 8/9) (as known from 3GPP TS 36.212 mentioned previouslyherein) depending on the component carrier bandwidth:

TABLE 4 System Bandwidth Size of DCI format 0/1A Size of DCI format 0/1A[MHz] in FDD [bits] in TDD [bits] 1.4 21 23 3 22 25 5 25 27 10 27 29 1527 30 20 28 31

If a CIF field is added these formats 0/1A, as defined in 3GPP LTE-A(Release 10), the size of formats 0/1A in 3GPP LTE-A (Release 10) hasadditional three bits more to account for the CIF field.

Hence, as apparent from the different examples given above, the minimuminformation that needs to be signaled in the component carrier(de)activation message is the target UE ID to identify the intendedrecipient of the component carrier (de)activation message. If the targetUE ID is a C-RNTI of the destined user equipment, this means that 16bits are required for the target UE ID. For each target componentcarrier ID, additional ┌ log₂ (N−1)┐ bits are required. Eachactivation/deactivation flag requires one additional bit.

For example, in case of using one single cell-specific RNTI foridentifying the DCI format, assuming that there are N=5 configuredcomponent carriers, of which N−1=4 need to be indicated in the targetcomponent carrier ID field (the anchor carrier is always in activestate) and that the activation state for one component carrier is to besignaled only, this would imply that the DCI payload of the componentcarrier (de)activation message requires 16 bits for the cell-specificRNTI (target UE ID), 2 bits for the indication of the target componentcarrier (target component carrier ID) and one bit of theactivation/deactivation flag ((De)Act flag), which is 19 bits in total.Hence, assuming the smallest component carrier bandwidth of 1.4 MHz atleast two “extra” bits are available for further use. If theactivation/flag can be omitted due to using two cell-specific RNTI foridentifying the DCI format and the activation state, even threeadditional bits would be unused for the smallest component carrierbandwidth of 1.4 MHz.

In another embodiment of the invention, and in accordance with thesecond aspect of this invention, the component carrier (de)activationmessage is provided within a transport block on the physical downlinkshared channel (PDSCH). For example, the component carrier(de)activation message may be a MAC signaling message for activating anddeactivating downlink component carriers. In one exemplaryimplementation, the component carrier (de)activation message is providedin form of a new MAC control element identified by a specific LCID. Thisnew MAC control element carries the (de)activation information of whichconfigured downlink component carrier(s) of the mobile terminal shall beactivated and/or deactivated.

The MAC control element for the component carrier (de)activation messagemay be octet aligned, i.e. consist of a multiple of 8 bits (1 byte). Theactually size of the MAC control element for the component carrier(de)activation may be determined by the number of downlink componentcarriers that can be configured in the user equipment. If there is a analways active primary component carrier provided, as for example in an3GPP LTE-A (Release 10) system, this number of downlink componentcarriers is the number of secondary component carriers that can beconfigured in the user equipment.

In one exemplary embodiment, the (de)activation information within thecomponent carrier (de)activation message is provided as a bitmap. Eachbit of the bitmap represents an activation/deactivation flag for one ofthe downlink component carriers (or secondary component carriers, if aprimary component carrier is provided). For example, a bit set to 0could mean that the corresponding component carrier is to be deactivatedand the bit set to 1 could mean the activation of the component carrier,or vice versa.

Alternatively, the bits of the bitmap may also indicate the activationstate of the component carriers associated to the respective bits. Forexample, a bit set to 0 could mean that the activation state of thecorresponding component carrier is the configured but deactivated stateand the bit set to 1 could mean the activation state of the componentcarrier is active state (“configured and activated”), or vice versa. Inthis case, the mobile terminal would determine whether there is a changeof the activation state for a component carrier and activates ordeactivates the respective component carrier accordingly. If the numberof downlink component carriers that need to be distinguished in the islower than nine, only one octet of payload is needed for signaling thebitmap.

For example currently in 3GPP standardization with respect to 3GPP LTE-A(Release 10), it is assumed that a maximum of five component carriers inthe downlink can be aggregated. One of these five downlink componentcarrier is designated as the downlink primary component carrier, whichis always active and hence cannot be activated or deactivated. Thiswould leaves four additional downlink secondary component carriers(SCCs) in the downlink that can be configured in a user equipment andthus can be activated/deactivated. Hence, in one exemplary embodiment ofthe invention, the bitmap has a size of four bits corresponding to themaximum of four downlink secondary component carriers. This leaves fouradditional bits for further signaling in the MAC control element thatmay be used for triggering the transmission of SRSs and/or powerheadroom reports (PHRs) by the user equipment.

An exemplary component carrier (de)activation message that is defining anew DCI format for transmission on the PDCCH and for use in a 3GPP LTE-A(Release 10) is shown in FIG. 25. Similar to the other DCI exemplaryformats proposed herein, the messages comprises ain identification ofthe target user equipment. Furthermore, there are 4 flags provided thatform the bitmap. Each of the flags is associated to a respectivedownlink component carrier and is used for (de)activation thereof asoutlined above. Please note that this 4 bit-bitmap may also form thepayload of a MAC control element that is used to implement the componentcarrier (de)activation message.

Furthermore, it may be advantageous to ensure that there is a one to onemapping between each bit of the bitmap and the corresponding componentcarrier it refers. This type of correspondence may be for examplerealized by using the component carrier index (CI) used in componentcarrier configuration message transmitted via RRC. For instance, thehighest bit (first bit) of the bitmap could refer to the highest (orlowest) component carrier index, the second highest (second bit) of thebitmap could refer to the second highest (second lowest) componentcarrier index, etc. This way a one-to-one correspondence between theindividual bit positions in the bitmap and the component carriers theyrefer to can be established.

As mentioned above, component carrier (de)activation message, e.g. inform of an MAC control elements, is included in the transport block inthe PDSCH of one of the downlink component carriers. Hence, forreception of the component carrier (de)activation message, the userequipment needs to successfully decode the transport block in order to“obtain” the (de)activation information. The transport block containingthe component carrier (de)activation message (as well as other transportblocks on the PDSCH) may be transmitted using an HARQ protocol in orderto ensure its successful delivery and decoding at the user equipment. Ifthe transport block is not decoded successfully by the user equipment'sdecoder, HARQ retransmissions for a transport block (including thecomponent carrier (de)activation message) increase the time betweenactual issuing of a (de)activation command by the eNodeB and thereception of the (de)activation command at the user equipment. In thecase of using a MAC control element for component carrier (de)activationthis could mean delayed activation and deactivation with possiblenegative effects on scheduling and power saving of the user equipment.

In order to minimize the possibility of retransmissions, and thusavoiding the possible negative effects mentioned above, the transmissionof the component carrier (de)activation message may be for examplerestricted to the most reliable of the downlink component carriers. Inactual deployments this most reliable component carrier may be—in mostcases—the primary component carrier (PCC) of the user equipment. The PCCis also associated with Radio Link Failure (RLF), therefore it needs tobe a reliable component carrier since otherwise the user equipment couldnot establish a reliable connection to the network. Furthermore, it isthe only component carrier that is always active, i.e. cannot bedeactivated or activated. Hence, in one implementation example, thecomponent carrier (de)activation message is transmitted by the eNodeB onthe user equipment's PCC to the user equipment. Hence, if the componentcarrier (de)activation message is implemented as a MAC control element,the transmission of the MAC control element for component carrier(de)activation to the PCC reduces the chances of delayed activation anddeactivation of the secondary component carriers of the user equipment.

In the sections above (de)activation of configured downlink componentcarriers using either L1 signaling (i.e. a new DCI format on the PDCCH)or L2 signaling (i.e. signaling the component carrier (de)activationmessage in a transport block on the PDSCH, e.g. in form of a MAC controlelement) have been described. The following considerations apply to bothaspects of this invention.

When eNodeB is deactivating a configured downlink component carrier, theuser equipment may deactivate the indicated component carriersimmediately after reception of the deactivation command (componentcarrier deactivation message). If the user equipment receives adeactivation message for a configured component carrier where thetransmission of a transport block using the HARQ protocol (i.e. one ofthe HARQ processes is (re)transmitting a transport block on the PDSCHwhen receiving the deactivation command) is not finished, i.e.retransmissions are still pending for the transport block, the immediatedeactivation of the component carrier would stop HARQ retransmission andthe transport block would be lost.

As the HARQ protocol of Layer 2 is also terminated in the eNodeB, theeNodeB is aware of the ongoing HARQ retransmissions of the userequipment on the configured downlink component carrier and may thus notdeactivate a component carrier, where a transport block has not yetsuccessfully received by the user equipment, i.e. not yet (positively)acknowledged by the user equipment. This would have however imply thatthe eNodeB may need to send an individual deactivation messages for eachcomponent carrier, even though when deactivation would be possible to besent within one signaling message, since the HARQ operation on thedifferent downlink component carriers and HARQ processes of the HARQprotocol may not be aligned.

Therefore, in another embodiment of the invention, in order to alloweNodeB to combine several deactivation commands within one signalingmessage without causing loss of transport blocks, the user equipment isnot deactivating a component carrier right after receiving adeactivation command for the given configured component carrier.Instead, the user equipment determines the HARQ protocol status for thecomponent carrier (i.e. determines whether there are still anyretransmission(s) of a transport block(s) pending) and deactivates thecomponent carrier upon a pending transmission having been successfullyfinished (i.e. having been (positively) acknowledged by the userequipment or the maximum number of retransmissions has been reached forthe pending transmission.

This operation of the downlink component carrier deactivation is alsoadvantageous in terms of the eNodeB not needing to wait for anacknowledgement on each of the transmissions ongoing on the componentcarriers to be deactivated, so that the actual deactivation command fora component carrier can occur several sub-frames (TTIs) earlier sincethe user equipment does not need to wait for the acknowledgement of thelast transmission.

Especially when (de)activation signaling is done by MAC signaling thisis beneficial for power saving at the user equipment.

In the following paragraphs, different exemplary implementations andembodiments regarding the design of the component carrier (de)activationmessage format will be discussed in further detail.

In one exemplary implementation of the component carrier (de)activationmessage format (i.e. the DCI format) is used for controlling theactivation state of one downlink component carrier configured by amobile terminal. In this embodiment, one of the “Extra” bits/flags asfor example shown in FIG. 9 or FIG. 10 is used to request the mobileterminal to send channel quality feedback for the controlled downlinkcomponent carrier. This may be especially suitable in situations wherethe downlink component carrier is activated (configured but activatedstate→active state). For this purpose the component carrier(de)activation message comprises in its payload a “CQI request flag”,that when set triggers the provision of channel quality feedback for thedownlink component carrier activated by the component carrier(de)activation message. An example for a component carrier(de)activation message according to one embodiment of the inventionincluding a CQI request flag is shown in FIG. 16.

In one more detailed implementation example according to an embodimentof the invention, the channel quality feedback in form of CQI, PMI(Precoding Matrix Indicator) or RI (Rank Indicator) could be transmittedon resources of a physical uplink control channel (PUCCH). Ifconsidering an implementation in a 3GPP based system, like 3GPP LTE-A(Release 10), the possible PUCCH payload may be quite restricted since asingle resource block shares PUCCHs from multiple user equipments.Therefore, the channel quality feedback may for example signal awideband CQI/PMI assuming a Rank=1 transmission.

The transmission of the channel quality feedback message can further beconsidered by the base station as an acknowledgement for the mobileterminal having successfully received the component carrier(de)activation message, respectively for the mobile terminal havingexecuted the activation command comprised in the component carrier(de)activation message.

Furthermore, the channel quality feedback (e.g. the CQI/PMI) may be sentby the mobile terminal a known time interval (e.g. 4 ms) after havingreceived the sub-frame (PDCCH) containing the component carrier(de)activation message. In 3GPP LTE (Release 8/9) in FDD mode, the timespan between reception of a sub-frame (PDCCH) and a corresponding uplinktransmission is 4 ms (for TDD the time span determination as morecomplicated). The time span between reception of the sub-frame (PDCCH)containing the component carrier (de)activation message and thetransmission of channel quality feedback in uplink may alternatively beconfigured by RRC signaling. For instance, it may be desirable to givethe mobile terminal more than 4 ms (e.g. 8 ms or 12 ms) to send thechannel quality feedback, in order to allow the mobile terminal toperform an accurate channel quality measurement to obtain an adequateaccuracy of the CQI/PMI after activating the respective downlinkcomponent carrier(s).

As to the uplink resources for the transmission of the channel qualityfeedback, the resource on the PUCCH may be for example the same PUCCHresource that is given to the mobile terminal for the periodic CQIreporting. This PUCCH resource may be configured by the base station viaRRC signaling when configuring the downlink/uplink component carrier.

Alternatively, the channel quality feedback may also be transmitted on aPUCCH or PUSCH resource that is predetermined by the base station, e.g.as part of the RRC component carrier configuration message. A furtheralternative is that the uplink resource for transmitting the channelquality feedback is indicated by one or more of the “extra” bits thatare available in the payload of the component carrier (de)activationmessage. This implementation can be beneficially exploited in case of alarge component carrier bandwidth (as discussed above with respect toFIG. 9 and Table 4), where several bits may be unused and available tospecify the feedback resources in the uplink. The two latteralternatives may also be combined in that the RRC component carrierconfiguration message configures a set of uplink resources for thechannel quality feedback (CQI/PMI/RI), and the (de)activation messagecomprises a feedback resource field that selects one out of theavailable configured uplink resources. An example for an extendedcomponent carrier (de)activation message including a CQI request flagand a CQI feedback resource field is shown in FIG. 17.

Moreover, in case that the uplink resource for the channel qualityfeedback is signaled or pre-configured, the channel quality feedback ispreferably determined according to the configured aperiodic CQI modeand/or the configured downlink transmission mode of the downlinkcomponent carrier that is indicated by the component carrier(de)activation message.

Furthermore, in another embodiment, channel quality feedback may also bemultiplexed with further physical layer messages or signals, such asHARQ feedback (ACK/NACK), SR or SRS, on the assigned uplink resource. Incase only physical layer messages but no transport block data issignaled on the uplink resource, no HARQ process (HARQ protocol) needsto be employed for the transmission, so that HARQ related controlinformation (such as NDI, HARQ process ID, etc.) may not need to besignaled for the transmission.

In another embodiment of the invention, the component carrier(de)activation message may be used to trigger/activate periodic channelquality feedback (periodic CQI/PMI/RI transmission) with respect to thesub-frame where the component carrier (de)activation message for theaction of the downlink component carrier is received.

In this embodiment of the invention, procedure as known from 3GPP LTE(Release 8/9) is reused. Accordingly periodic CQI/PMI/RI is basicallytransmitted in sub-frames having a sub-frame number satisfying thecondition:

(N _(Subframe) −N _(OFFSET,CQI))mod N _(Periodicity)=0  (2)

where

N _(Subframe)=10×n _(f) +└n _(s)/2┘  (3)

and where n_(f) is the system frame number, and n_(s)={0, 1, . . . , 19}is the slot index within the frame. It should be noted that the relationhere is a simplified mechanism to explain the timing principle, howeverthere are special cases that render the timing slightly more complicated(see also 3GPP TS 36.213, “Physical layer procedures”, version 8.8.0(Release 8) or 9.0.1 (Release 9), section 7.2.2 for further details, thedocuments being available at http://www.3gpp.org and the sections beingincorporated herein by reference).

In one embodiment of the invention, in case the component carrier(de)activation message from the base station comprises a CQI flag beingset, the mobile terminal is providing a single (aperiodic) CQI report(One-time CQI) at a given offset of k sub-frames relative to thesub-frame of the (de)activation message and starts signaling periodicCQI reports in the sub-frames and on the PUCCH resources that have beenconfigured for the component carrier activated by the component carrier(de)activation message. An exemplary scenario according to thisembodiment of the invention for visualizing this procedure is shown inFIG. 22, where after the activation of downlink (DL) component carrier(CC) 2 (DL CC2) by means of the CC activation message, a CQI report(One-time CQI for DL CC2) is sent after k=4 sub-frames after havingreceived the CC activation message for DL CC2 in which a CQI requestflag is included and set, while the subsequent CQI reports for DL CC2are signaled in the sub-frame number indicated by the N_(OFFSET,CQI) onthe uplink resources and with the periodicity N_(Periodicity) configuredfor periodic CQI reporting. Furthermore, upon the base station signalinga CC deactivation message for DL CC2 in which a CQI request flagincluded and not set, the mobile terminal deactivates DL CC2 again andstops periodic CQI reporting.

In another embodiment of the invention, a new way of calculatingN_(OFFSET,CQI) is employed so that the first periodic CQI report of themobile terminal is transmitted at a given offset k relative to thecomponent carrier activation message. In the periodic CQI reportingprocedure of 3GPP LTE (Release 8/9) indicated above, the transmission ofthe CQI/PMI/RI thus depends on the system-wide sub-frame number,irrespective of the sub-frame number of the sub-frame comprising thecomponent carrier (de)activation message. In order to start the periodicCQI/PMI/RI report as early as possible, in this embodiment the conditionis modified as follows. Periodic CQI/PMI/RI is transmitted in asub-frame the sub-frame number of which is satisfying the (updated)conditions (2) and (3) above as known from 3GPP TS 36.213, howeverchanging the definition of the offset N_(OFFSET,CQI) so that it doesn'trefer to sub-frame number 0, but to the sub-frame number in which thecomponent carrier (de)activation message has been received, i.e.

N _(OFFSET,CQI)=mod(N _(Subframe,Activation) +k,N_(Subframe,Max)+1)  (4)

where N_(Subframe,Activation) is the sub-frame number of the sub-framein which the component carrier (de)activation message triggering(activating) CQI/PMI/RI reporting for the activated downlink componentcarrier, and N_(Subframe,Max) is largest sub-frame index. In 3GPP LTE(Release 8/9), the system frame number ranges from 0 to 1023, eachsystem frame comprises slot 0 to 19; consequentlyN_(Subframe,Max)=10×n_(f,Max)+└n_(s,Max)/2┘ or N_(Subframe,Max)=10239.In the condition (4), the offset k added to N_(Subframe,Activation) maybe for example configurable or static.

In one example, k=4 so as to ensure that the earliest channel qualityfeedback transmission occurs 4 sub-frames after the sub-frame number ofthe sub-frame in which the component carrier (de)activation messagetriggering (activating) CQI/PMI/RI reporting for the activated downlinkcomponent carrier(s). However, if the channel quality feedback is to beprovided with a larger offset (i.e. later), it can be necessary toincrease the parameter k, as mentioned before. For example, kε{4, 6,8,10,12}.

FIG. 23 is exemplarily highlighting the mobile terminal's behavioraccording to this embodiment of the invention in response to thereception of a component carrier (de)activation message comprising a CQIrequest flag being set using the updated periodic CQI reportingprocedure. Upon the base station activating DL CC2 by means of the CCactivation message received in sub-frame number N_(Subframe,Activation),the offset N_(OFFSET,CQI) is assumed to be set according to condition(4) and sends the CQI report for DL CC2 k sub-frames later, which ishere 4 sub-frames, respectively 4 ms, after having received the CCactivation message on the PUCCH resources configured for periodic CQIreporting. Subsequently, the mobile terminal provides periodic CQIreports for DL CC2 with periodicity N_(Periodicity) configured forperiodic CQI reporting, until the CC deactivation message of the basestation deactivates DL CC2.

The benefit of the modified periodic CQI/PMI/RI reporting procedurediscussed in the previous paragraphs is that the first CQI/PMI/RI reportis received very early after having activated the downlink componentcarrier, which may be helpful for the scheduler of the base station toschedule transmission on the activated downlink component carrier, andthat subsequent CQI reports are transmitted according to the configuredperiodicity.

Since depending on the configuration of the periodic CQI/PMI/RI reportit can happen that it is unclear what kind of transmission rank (thetransmission rank determines the precoder matrix dimension for MIMOtransmissions) is used, preferably the first such periodic CQI/PMIreport consists of a wideband CQI/PMI report assuming Rank=1.Alternatively, the first CQI/PMI/RI report after activation of thedownlink component carrier(s) consists of a Rank indicator (RI),followed by the CQI/PMI in the next report transmitted according to theperiodic CQI/PMI/RI configuration as discussed in the precedingparagraphs.

The cases where the periodic CQI/PMI/RI report is configured as at leastwideband CQI/PMI and sub-band CQI as per 3GPP TS 36.213, section 7.2.2can be treated applying the above mentioned timing offset and firstCQI/PMI/RI report content principles mutatis mutandis. Particularly, itshould be avoided to send a subband CQI as the first CQI report afteractivation.

In addition to the CQI request flag or alternatively thereto, the unusedbits (extended use) of the component carrier (de)activation message mayalso be used to trigger the transmission of sounding reference symbols(SRS) in the uplink or a power headroom report (PHR).

In a further embodiment of the invention a “SRS request” flag may beincluded in the component carrier (de)activation message as shown inFIG. 19. The SRS request flag when set by the base station, requests themobile terminal to start transmission of sounding reference symbols(SRS) on the linked uplink component carrier(s) that is/are linked tothe downlink component carrier(s) activated by the component carrier(de)activation message. If the component carrier (de)activation messageis activating uplink component carrier(s), the mobile terminal startssending sounding reference symbols (SRS) on the activated uplinkcomponent carrier(s). Triggering SRS instead of CQI may be particularlybeneficial in case of time division duplex (TDD) systems where thechannel can be assumed to be reciprocal, so that the channel estimationfor the uplink based on SRS can be used for the channel estimation forthe downlink as well.

Similar to the inclusion of a CQI request flag, the inclusion of the SRSrequest flag is advantageously included in component carrier(de)activation messages that indicate a component carrier activation. Incase of deactivation, the bits for the either flag can be reserved forother signaling. Alternatively, SRS request flag (or an SRS field havingmore than one bit) may also be present in component carrier(de)activation messages that deactivated a component carrier, and may beused to point to a new component carrier where the mobile terminalshould subsequently expect or transmit signals that so far have beentransmitted on the component carrier that is being deactivated.

In a further alternative implementation the bits for the SRS requestflag and the CQI request flag within a component carrier (de)activationmessage could be used to indicate a time offset between the reception ofthe (de)activation command and the execution of the (de)activationcommand. Alternative uses of extra bits are to signal whether thereception of the command should be acknowledged by the receiver(explained below).

The signalling of SRS enabling/disabling as described above can also berealized in accordance with the second and third aspect of theinvention: Using MAC signaling. SRS information that indicates for whichcomponent carriers(s) in the uplink SRS(s) should be transmitted by theuser equipment. For example, the SRS information that indicate the(de)activation of the SRS(s) may be for example provided in a new MACcontrol element, similar as described for the component carrier(de)activation message. This MAC control element contains a bitmapsimilar to the MAC control element for the downlink component carrier(de)activation as described above. Each bit in the bitmap refers to oneuplink component carrier of the user equipment for which the SRStransmission should be started/stopped. Alternatively, one can considerthe bits of the bitmap associated to respective ones of the configureddownlink component carriers. In this case the bit for a given downlinkcomponent carrier indicating the (de)activation of SRS will cause theuser equipment to (de)activate the transmission of SRS on the uplinkcomponent carrier linked to the given downlink component carrier. Forexample, a bit of the bitmap being set to 0 may indicates not totransmit periodic SRS on the associated (linked) uplink componentcarrier, respectively to stop transmitting periodic SRS; while a bit setto 1 would indicate to activate periodic SRS transmission on theassociated (linked) uplink component carrier (or vice versa).

If there are enough bits unused in the MAC control element for downlinkcomponent carrier (de)activation these bits can be used for the SRS(de)activation as described above. In the example given above, assumingthat there are five downlink component carriers aggregated in thedownlink, of which four downlink component carriers can be activated ordeactivated (i.e. one PCC and four SCCs are provided), four bits areneeded for the (de)activation of the downlink secondary componentcarriers. Considering the MAC control element to have the size of oneoctet, this leaves additional four bits that are not used which can beused for the bitmap to signal SRS (de)activation as described above.

An exemplary MAC control element which allows simultaneous(de)activation of downlink component carriers and de)activation of SRStransmissions by the user equipment is shown in FIG. 24. The first fourbits of the octet define the bitmap for downlink component carrier(de)activation, while the second four bits thereof define the bitmap forthe (de)activation of SRS transmission by the user equipment. Anadvantage of combining both bitmaps for (de)activation of SCCs and(de)activation of SRS transmission within one MAC control element may bethat periodic SRS transmission on the linked uplink component carrier(s)can start simultaneous with downlink SCC activation. This avoidspossible delays that could occur when both functions are signalled inseparate MAC control elements and reduces overhead. It should be noticedthat both component carrier (de)activation and SRS enabling/disablingcan be still signalled independently even when they are signalled in thesame MAC control element. FIG. 26 shows another exemplary implementationof a component carrier (de)activation message in form of a new DCIformat that allows simultaneous (de)activation of downlink componentcarriers and de)activation of SRS transmissions by the user equipment.Basically, the bitmask as shown in FIG. 24 is signaled in this componentcarrier (de)activation message together with an indication of the userequipment which is to receive the component carrier (de)activationmessage.

In another embodiment of the invention in case a downlink componentcarrier is activated by the base station, the activation of the downlinkcomponent carrier triggers a power headroom report (PHR) by the mobileterminal. The mobile terminal may send the triggered PHR report on theresources assigned by a next uplink grant for this linked uplinkcomponent carrier to the base station. This may ensure that the basestation is informed on the path-loss situation for the linked uplinkcomponent carrier in the next uplink transmission of the mobile terminalon the linked uplink component carrier. This may be beneficial since thelinked uplink component carrier has most likely not been used at leastfor a longer time period prior to the activation of the linked downlinkcomponent carrier. The power headroom reports from the mobile terminalenable the base station to improve scheduling decisions.

Alternatively, in another embodiment of the invention, the detailed CQIreporting, SRS transmission, PHR reporting etc. in response to acomponent carrier (de)activation may also be configured by the basestation using RRC signaling or may use a pre-determined configuration(known to base station and mobile terminal).

Upon successful detection of a (de)activation command, the mobilestation may confirm the execution of the (de)activation command bysending a confirmation message (acknowledgement) in uplink. In oneembodiment of the invention, the following method is used to acknowledgethe successful decoding of the component carrier (de)activation message,respectively the execution of the (de)activation command:

-   -   Sending an acknowledgement (also referred to as “HARQ-ACK” in        the 3GPP terminology) in case of deactivation of a component        carrier, where the resource for the acknowledgement transmission        follows the principles of 3GPP LTE (Release 8/9) for sending        HARQ-ACK in case of a downlink data transmission (PDSCH) as        defined in 3GPP TS 36.213, section 10. In brief, the PUCCH        resource for the HARQ-ACK is determined according to the PDCCH        resource where the (de)activation message is transmitted. In        this case, the eNodeB can do a power detection to check whether        HARQ-ACK was transmitted on the expected resource or not.    -   Sending an acknowledgement (also referred to as “HARQ-ACK” in        the 3GPP terminology) in case of activation of a component        carrier without requesting a quick CQI, where the resource for        the acknowledgement transmission follows the procedure of 3GPP        LTE (Release 8/9) for sending HARQ-ACK in case of a downlink        data transmission as defined in 3GPP TS 36.213, section 10. In        this case, the eNB can do a power detection to check whether        HARQ-ACK was transmitted on the expected resource or not.    -   Sending the CQI report in case of activation of a component        carrier and CQI request flag being set in the component carrier        (de)activation message. In this case, the eNodeB can do a power        detection to check whether CQI report was transmitted on the        expected resource or not.    -   Triggering a PHR in case of activation of a component carrier.    -   As indicated above, PUCCH feedback resources for the        acknowledgement may be for example determined by the mobile        terminal in the same fashion as provided I the 3GPP LTE (Release        8/9) procedure, as if the component carrier (de)activation        message schedules a PDSCH transmission, e.g. by DCI format 1A        (which is may have the same size as the component carrier        (de)activation message). Furthermore, as eNodeB is aware of        whether the user equipment will send an acknowledgement        (HARQ-ACK) or a CQI report, the eNodeB can monitor the        respective uplink resources on which the acknowledgement or CQI        report is expected from the user equipment.

Optionally, the user equipment may also send a NACK (HARQ NACK) in caseof not having decoded the component carrier (de)activation messageprocedure of 3GPP LTE (Release 8/9) for sending HARQ-NACK in case of adownlink data transmission as defined in 3GPP TS 36.213, section 10.

FIG. 20 shows an exemplary scenario according to an exemplary embodimentof the invention, where an Activation and a Deactivation RNTI areconfigured for the activation, respectively deactivation of componentcarriers. In this example, upon activation of one of the componentcarriers by the CC activation message (Activation RNTI), the userequipment synchronously signals an HARQ-ACK to the eNodeB to acknowledgethe successful decoding of the CC activation message. The HARQ-ACK issent with a given offset to the CC activation message (i.e. PDCCHcontaining same), for example after 4 ms. Similarly, upon the basestation deactivating the component carrier again by means of the CCdeactivation message (Deactivation RNTI), the user equipment againacknowledges the deactivation by means of a HARQ-ACK that is againsynchronously sent in the uplink after 4 ms.

FIG. 21 shows another exemplary scenario according to a furtherexemplary embodiment of the invention, where an Activation and aDeactivation RNTI are configured for the activation, respectivelydeactivation of component carriers. Furthermore, the activation of oneof the component carriers by the CC activation message (Activation RNTI)is further requesting the user equipment to signal channel qualityfeedback for the activated downlink component carrier (CQI request flagbeing set in the CC activation message). Accordingly, the user equipmentsignals at a known timing relative to the CC activation message, here 4ms after receiving same, an CWI report to the eNodeB therebyacknowledging the successful decoding of the CC activation message. Uponthe base station deactivating the component carrier again by means ofthe CC deactivation message (Deactivation RNTI), the user equipmentagain acknowledges the deactivation by means of a HARQ-ACK that issynchronously sent in the uplink after 4 ms.

In case the eNodeB intents to increase uplink and downlink capacity atthe same time, in a further embodiment of the invention, the basestation may further activate a downlink component carrier that is linkedto an uplink component carrier that is currently not used for uplinktransmissions. There is no information as to channel quality for aninactive or configured but deactivated uplink component carrieravailable at the eNodeB. Consequently in this embodiment of theinvention, the activation of a downlink component carrier is furthertriggering sounding reference signal (SRS) transmission on the uplinkcomponent carrier(s) linked to the activated downlink componentcarriers(s). In this case no additional SRS request flag may be needed,but the start of signaling SRS on the uplink component carrier linked toa downlink component carrier activated by component carrier(de)activation message may be a default behavior of the mobile terminalin response to the activation of the downlink component carrier.

Similarly as for the CQI reporting, also the transmission of SRS is notin all cases beneficial/required. Therefore it should be possible thateNodeB enables/disables SRS transmission when activating downlinkcomponent(s). This could be achieved by including a flag in the(de)activation message which indicates whether user equipment isrequired to send SRS. It may be further configured or specified orsignaled whether such an SRS should be one-time only, or periodic. Ineither case, further “extra” bits can be used to define one or more ofthe SRS parameters such as bandwidth, comb, etc (refer to 3GPP LTE(Release 8/9) SRS parameters).

Of course, the component carrier (de)activation message may also bedesigned to allow the simultaneous transmission of a CQI request flag,triggering a PHR and/or a SRS request flag.

When user equipment monitors the PDCCH, there is always a certainprobability (false alarm rate) that the mobile terminal falsely detectsa PDCCH: the CRC check of the PDCCH may be correct even though the PDCCHwas not intended for this user equipment, i.e. CRC passes even thoughthere is a RNTI mismatch (unintended user). This so called false alarmmight happen, if the two effects of transmission errors caused by theradio channel and RNTI mismatch cancel each other. The probability of afalsely positive decoded PDCCH depends on the CRC length. The longer theCRC length, the lower the probability that a CRC-protected message isfalsely correct decoded. With the CRC size of 16 bit the false alarmprobability would be 1.5·10⁻⁵.

In case a user equipment falsely detects a PDCCH with a downlinkcomponent carrier (de)activation message indicating the deactivation ofcertain downlink component carrier(s) the user equipment would stopmonitoring PDCCH/PDSCH for those indicated downlink component carrier(s)and also stops reporting CQI measurements. Given the severe consequencesof such user equipment behavior, it is therefore desirable to decreasethe false alarm probability.

Each bit of virtual CRC can be assumed to halve the false alarm risk. Onthe other hand, each additional RNTI that is used increases the falsealarm risk linearly. For example, in case of employing four componentcarrier-specific activation-RNTIs and four component carrier-specificdeactivation-RNTIs, the false alarm risk is eight times higher than forthe case of a single CC-RNTI. On the other hand, using the altogethereight CC-RNTIs does not require the inclusion of a target CC ID field inthe DCI payload nor that of an Activation/Deactivation field. In most ofthe exemplary implementations that have been discussed above, thelargest target component carrier ID size is four bits. Consequently, theusage of eight component carrier-RNTIs without target component carrierID field results in a false alarm risk of 8/2⁴=0.5 times compared to therisk when a single CC-RNTI with a four-bit target component carrier IDfield is employed. The drawback is the increased cost of RNTI, and therestriction that multiple (de)activation messages are required to(de)activate multiple component carriers at the same time.

In one embodiment of the invention, it is therefore proposed that thedownlink component carrier (de)activation message comprises one or moreextra bits (in a CRC field) can be used as a virtual CRC to reduce thefalse alarm risk. These additional bit(s) are set to a known, predefinedvalue which is to be verified by the mobile terminal.

Another embodiment of the invention relates to the implementation of theabove described various embodiments using hardware and software. It isrecognized that the various embodiments of the invention may beimplemented or performed using computing devices (processors). Acomputing device or processor may for example be general purposeprocessors, digital signal processors (DSP), application specificintegrated circuits (ASIC), field programmable gate arrays (FPGA) orother programmable logic devices, etc. The various embodiments of theinvention may also be performed or embodied by a combination of thesedevices.

Further, the various embodiments of the invention may also beimplemented by means of software modules, which are executed by aprocessor or directly in hardware. Also a combination of softwaremodules and a hardware implementation may be possible. The softwaremodules may be stored on any kind of computer readable storage media,for example RAM, EPROM, EEPROM, flash memory, registers, hard disks,CD-ROM, DVD, etc.

It should be further noted that the individual features of the differentembodiments of the invention may individually or in arbitrarycombination be subject matter to another invention.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

1. A communication method comprising: generating a MAC control elementincluding a cluster of bits which indicates an activation/deactivationstatus of each of at least one secondary component carrier that is addedto a primary component carrier which is always activated, each of the atleast one secondary component carrier corresponding to one bit includedin the cluster of bits, and the one bit indicating that a correspondingsecondary component carrier should be activated or deactivated, whereinwhen any one bit among the cluster of bits indicates that itscorresponding secondary component carrier should be activated, thecluster of bits further indicates a sounding reference signal (SRS)transmission request; and transmitting the generated MAC controlelement.
 2. The communication method according to claim 1, wherein thecluster of bits consists of a single octet and contains at least oneunused bit.
 3. The communication method according to claim 1, whereinwhen the cluster of bits further indicates the SRS transmission request,the MAC control element instructs a terminal apparatus to activate asecondary component carrier and to transmit an SRS on the activatedsecondary component carrier.
 4. The communication method according toclaim 1, wherein the SRS transmission is periodic.
 5. The communicationmethod according to claim 1, wherein the primary component carrier andeach of the at least one secondary component carrier is a componentcarrier including a plurality of subcarriers.
 6. A base stationapparatus comprising: a generator which, in operation, generates a MACcontrol element including a cluster of bits which indicates anactivation/deactivation status of each of at least one secondarycomponent carrier that is added to a primary component carrier which isalways activated, each of the at least one secondary component carriercorresponding to one bit included in the cluster of bits, and the onebit indicating that a corresponding secondary component carrier shouldbe activated or deactivated, wherein when any one bit among the clusterof bits indicates that its corresponding secondary component carriershould be activated, the cluster of bits further indicates a soundingreference signal (SRS) transmission request; and a transmitter which, inoperation, transmits the generated MAC control element.
 7. The basestation apparatus according to claim 6, wherein the cluster of bitsconsists of a single octet and contains at least one unused bit.
 8. Thebase station apparatus according to claim 6, wherein when the cluster ofbits further indicates the SRS transmission request, the MAC controlelement instructs a terminal apparatus to activate a secondary componentcarrier and to transmit an SRS on the activated secondary componentcarrier.
 9. The terminal apparatus according to claim 6, wherein the SRStransmission is periodic.
 10. The terminal apparatus according to claim6, wherein the primary component carrier and each of the at least onesecondary component carrier is a component carrier including a pluralityof subcarriers.